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-B3 



Physiology 

by 
THE LABORATORY METHOD 

For Secondary Schools 



By WILLIAM J. BRINCKLEY, Ph.D. 

Vice-President and Professor of Biology in Austin College, Effingham, 111. 



Trafttarig flfastrateri 



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Chicago: 

AINSWORTH dr* COMPANY 

1902 




QP42. 



THfl-fBRAUV OF 

CONGRESS, 
Two Cowe* Rec««v€0 

AUG. 8 1902 

^ Copyright wmv 
fcLASS ^ XXo. Ho. 

t_ u- £ q # 

COPY 8. 



Copyright, 1902 
By William J. Brinckley 



All rights reserved 



PREFACE. 

A pbominent educator lias said that modern education 
consists of the three L's rather than of the three R's ; i. e., 
of the laboratory, the lecture, and the library. 

While this ideal cannot be realized in its fullness except 
in our universities and larger colleges, its basal principles 
are applicable to all grades of instruction. In other words, 
we study things and phenomena, not books. 

The lecture, the library, and the text are to confirm, 
extend, and supplement the work of the laboratory. The 
text-book becomes, then, not something to be learned by rote, 
but something to assist the pupil in his inquiry for truth, 
and should contain such a statement of the subject con- 
sidered as will answer all reasonable inquiries relative to an 
elementary notion of the subject considered. It should con- 
tain such information as will enable the student to complete 
and organize the facts gathered by observation in experi- 
ment, and as will awaken a desire to know more. 

In our enthusiasm over method we should not forget 
that we study to know, as well as to have power to do, and 
especially is this true in the study of the human body. We 
have the control and guidance of the most wonderful of 
mechanisms, and Avhile it is important that we use correct 
methods in obtaining information in regard to this mechan- 
ism, it is of vital importance that we possess sufficient knowl- 
edge of its structure and actions to secure to ourselves, under 
ordinary conditions, good health. Such certainly cannot be 
secured by a mere statement of facts of hygiene, but only 
by such a knowledge of the structure and principles of the 
body's normal action as will enable us to treat our bodies in 
a rational manner. 

The author has given a number of subjects a fuller 
treatment than is commonly given to them in works of this 
grade, as experience has shown that pupils cannot form a 



CONTENTS. 



CHAPTER PAGE 

I. Introduction ...... 1 

Experiments and Demonstrations. — Classes of bodies; 
surface features of the body; cavities of the body; 
systems of the body. 

Text.— Relation of the human body to other bodies; 
importance of the study of the lower animals; re- 
gions of the human body; cavities of the human 
body and their viscera; systems of the human 
body; apparatus of the human body. 

II. Microscopic Structure of the Human Body 14 

Experiments and Demonstrations. — Preparation and 
examination of tissues. 

Text. — Tissues: kinds, structure, origin, and distri- 
bution. 

III. Anatomical Elements .... 32 

Experiments and Demonstrations. — The cell: forms, 
structure, and phenomena. The fiber: kinds, struc- 
ture, and properties. 

Text. — The cell: size, form, structure, phenomena, 
and modes of multiplication. The fiber: varieties, 
structure, origin, properties, and distribution. 

IY. The Muscular System . . . .45 

Experiments and Demonstrations. — Arrangement; 
gross structure, microscopic structure; properties 
and muscle phenomena. 

Text. — Motion, need of; nature of muscular contrac- 
tion; arrangement of muscles; gross structure; 
microscopic structure; nature and phenomena of 
muscular contraction; muscular movements; mus- 
cular sense; exercise, kinds and hygiene of; ef- 
fects of narcotics and stimulants on muscles. 

V. The Nervous System .... 82 

Experiments and Demonstrations — Dissection and 
study of the brain, spinal cord, cranial nerves; mi- 
croscopic structure of parts studied; phenomena 
of nerve action. 

Text. — Need of the nervous system; divisions of the 
nervous system; cerebrospinal system, organs of; 
brain, spinal cord, cranial and spinal nerves, their 
structure, relation, and function. Sympathetic 
system: of what organs composed, structure, distri- 
bution and function. Cerebral localization, sen- 
sory and motor tracts; nerve centers: automatic, 

vii 



' CONTENTS. 

CHAPTER PAGE 

sense of taste, organs of; nature of sense; con- 
ditions of; use. 



XVII. The Sense of Smell . . . 379 

Text. — The nose: structure, relation, use; nature of 
sense; conditions of. 

XYIII. Vision .... . 384 

Experiments < 
the organs 
with light. 



Experiments and Demonstrations. — Examination of 
the organs of the apparatus of vision; experiments 
with light. 

Text. — Description of the apparatus of vision; theory 
of vision; hygiene of apparatus of vision. 



XIX. Heaeing 421 

Experiments and Demonstrations. — Examination of 
organs of hearing; experiments in acoustics. 

Text. — Description of the organs of hearing; nature 
of sound; how we hear. 

XX.. The Voice 439 

Experiments and Demonstrations. — Study of organs; 

how voice is produced. 
Text. — Description of the organs of voice; how voice 

is produced; hygiene of the voice. 

APPENDIX. 

I. Histological methods and reagents. 
II. General rules of dissection. 

III. Common tests. 

IV. Poisons; names; symptoms and antidotes. 
V. Contagious disease; how to disinfect. 

VI. Accidents. 
VII. List of apparatus. 
VIII. Books for reference. 



LIST OF ILLUSTRATIONS. 



Pig. 
1. Regions of the Body 








A. Anterior View. 


B. Posterior View. 


2. Transverse Section of Necturus 


3. Section of the Bod}- on Median Line (Plate I) 




4. Transverse Section of the Body (Plate I) 




5. Superficial Viscera 






C. Deep Viscera 








7. Systems of the Body (Diagram) 








8. Epithelial Tissue 








9. Ciliated Epithelium 








10. Columnar Epithelium 








11. Pavement Epithelium 








12. Prickle Cells 








13. Cross-Section of Skeletal Muscle 








14. Skeletal Muscle 








15. Unstriped Muscle 








1C. Heart Muscle 








17. White Fibrous Tissue 








18. Yellow Elastic Tissue 








19. Adipose Tissue 








20. Hyaline Cartilage 








21. Cellular Cartilage 








22. Bone, Transverse Section 








23. Bone, Long Section 








24. Gelatinous Tissue 








23. Glandular Tissue 








2G. Goblet Cells 








27. Amoeba 








28. Internal Cell Division 








29. The Centrosome 








30. Indirect Cell Division . 








31. Stages of Development 








32. The Typical Cell 








33. Muscle Curve Apparatus 








34. Forms of Muscles 








34a. Classes of Levers 








35. Muscles of the Neck (Plate II) 








36. Muscles of the Face (Plate II) 








37. Muscles of Mastication (Plate II) 









Page. 



G 



Xll 



LIST OF ILLUSTRATIONS. 



38. 
39. 
40. 
41. 
42. 
43. 
44. 
45. 
46. 
47. 
48. 
49. 
50. 
51. 
52. 
53. 
54. 
55. 



56. 

57. 

58. 

59. 

60. 

61. 

62. 

63. 

64. 

65. 

66. 

67a 

675, 

68. 

69. 

70. 

71. 

72. 
73. 

74. 
75. 
76. 
77. 
78. 
79. 



Muscles of Mastication (Plate II) 

Muscles of the Back (Plate III) 

Muscles of the Back (Plate III) 

Muscles of the Trunk (Plate IV) 

Abdominal Muscles (Plate IV) 

Muscles of the Arm (Plate V) 

Muscles of the Forearm (Plate V) 

Muscles of the Thigh (Plate VI) 

Muscles of the Leg (Plate VI)" 

Muscles of the Leg (Plate VI) 

Typical Muscle 

The Muscle Fiber 

Distribution of Blood Vessels to Muscle Fibers 

Distribution of Nerves to Muscle Fibers 

Muscle Curve ..... 

Tetanus Curve .... 

General View of Spinal Cord 

Transverse Section of Spinal Cord in Different Regions 

(a) Cervical 

{b) Dorsal 

(c) JLumbar 
Motor and Sensory Tracts of Spinal Cord 
Distribution of Spinal Nerve 
Origin of Spinal Nerves 
Old Idea of Reflex Action 
Mechanism of Reflex Action 
Section of Brain on Median Line 
Inferior Surface of Brain 
Superior Surface of Brain 
Ventricles of the Brain 
Transverse Vertical Section of the Brain 
Vertical Section of the Brain 
Coverings of the Brain 
Coverings of the Brain 
Side View of Medulla 
Posterior View of Medulla . ■ 
Relation of Fibers of the Cerebro-Spinal System (Plate 

VII) 

Sensory and Motor Tracts of the Cord (Plate VIII) 

Course of Fibers in Brain and Spinal Cord (Plate IX) 

Course of Fibers in Brain (Plate X) 

Superficial Origin of Cranial Nerves 

Deep Origin of Cranial Nerves 

Lobes of the Brain (Plate XI) 

Microscopic Structure of the Brain 

Cerebral Localization (Plate XII) 

Sympathetic Nerves, Plexuses 



LIST OF ILLUSTRATIONS. 



80. Sympathetic Nerves . 




81. Section of Pneumogastric Nerves 




82. Nerve Fibers. 




(a) Medullated 




{b) Non-medullated 




S3. Nerve Cells . 




84. The Olfactory Bulb 




85. The Neuron .... 




86. The Skeleton . 




87. Side View of the Skull 




88. Front View of the Skull 




89. Base of Skull Exterior 




90. Base of Skull Interior . 




91. Occipital Bone 




92. Sphenoid Bone 




93. Temporal Bone 




94. Superior Maxillary 




95. Inferior Maxillary 




96. The Spine .... 




97. Parts of the Vertebra. 




(a) Side View 




(b) Seen from Below 




98. The Atlas ... 




99. The Axis . 




100. The Trunk .... 




101. The Scapula .... 




102. The Humerus . . • 




103. The Radius and Ulna . 




104. The Carpal and Metacarpal Bones 




105. The Pelvis .... 




106. The Femur . 




107. The Tibia and Fibula . 




108. The Foot .... 




109. Longitudinal Section of Long Bones 


i . 


110. The Alimentary Canal . 




111. The Pharynx . 




112. The Peritoneum 




113. Cardiac Glands . 




114. Pyloric Glands . 




115. Diagram of Newrous Mechanism of Alimentary Canal 


116. Mucous Membrane of Small Intestine 


117. Longitudinal Section of Villus . . . . 


118. Cross-section of Villus . 




119. The Salivary Glands . 




120. The Sublingual Gland . 




121. The Liver 




122. Structure of the Lobule of Liver 





XIV 



LIST OF ILLUSTRATIONS. 



123. Hepatic Cells .... 

124. The Portal Circulation 

125. Opening of Hepatic and Pancreatic Duct 

126. The Pancreas and Spleen 

127. Diagram of Circulation (Plate XTII) . 

128. Position of the Heart . 

129. The Heart (Plate XIV) 

130. Section of Heart to Right Auricle and Ventricle (Plate 

XIV) 

131. The Principal Arteries and Veins (Plate XV) 

132. Diagram of the Relative Area of Total Cross-section of the 

Arteries, Capillaries, and Veins . 

133. Artery, Cross-section .... 

134. Capillaries (Tail of Tadpole) . 

135. Mechanism of Circulation 

136. The Pulse Curve . 

137. Blood Corpuscles .... 

138. The Lymphatic Duct . . 

139. Structure of Lymphatic Gland 
140a.The Lungs ..... 
1406. Microscopic Structure .... 

141. The Diaphragm . 

142. The Skin 

143. Vertical Section of Hair Follicle 

144. Vertical Section of Hair Follicle (Magnified) 

145. The Finger Nail .... 

146. Magnified Section through Nail 

147. The Tooth, Vertical Section . 

148. Longitudinal Section of Kidney 
149a.Malpighian Body . 
1496. Microscopic Structure of the Kidney 

150. Tactile Corpuscles .... 

151. The Tongue ..... 
152a. The Papillae of the Tongue . 
1526. Vertical Section of the Circumvallate Papillae 

153. Taste Bulb . . . . 

154. Nasal Fossa and Distribution of Olfactory Nerve 

155. Section through Nasal Fossa . 

156. Olfactory Cells ..... 

157. Lachrymal Apparatus . 

158. Coats of the Eyeball .... 
159a. Diagram of the Elementary Structure of the Retina 
1596. Layers of the Retina . 

160. Blood Vessels of Eyeball (Plate XVI) 

161. Muscles of the Eye 

162. Irradiation, Astigmatism, Test Type, Test for the "Blind 

Spot," Defective Visual Judgment 



406 



LIST OF ILLUSTRATIONS. 



XV 



163. Optics of Vision ..... 

164. The Nervous Apparatus of Vision in Man (Plate XVII) 

165. The Theory of Color Vision . 

166. General View of the Ear 

167. The Internal Ear .... 

168. Structure of the Cochlea 

169. Section through One of the Coils of the Cochlea 

170. Auditory Hairs ..... 

171. The Larynx, Posterior View (Plate XVIII) . 

172. Anterior of the Larynx (Plate XVIII) 

173. Ventricles of the Larynx (Plate XVIII) 

174. The Vocal Cords (Plate XVIII) 



408, 409 
420 
414 
423 
427 
429 
430 
433 
442 
442 
442 
442 



APPENDIX. 



175. 
176. 
177. 
178. 

179. 

180. 



181. 



Parts of the Microscope ..... 458 

Illustrations of Various Disease Germs . . . 482 

The Xovy Apparatus for Formaldehyde Disinfection , 487 

Diagram Showing Relative Number of Deaths from Va- 
rious Diseases ...... 489 

Low "Water in Wells and Sickness from Typhoid Fever in 

Michigan ....... 492 

Resuscitation ....... 495 

(a) Inspiration. 

(b) Expiration. 

Treatment of the Drowned . 497 

Position 1. 
Position 2. 
Position 3. 



Physiology 

By the Laboratory Method, 



CHAPTER I. 

EXPERIMENTS AND DEMONSTRATIONS. 

Classes of Bodies. — 1. Examine carefully a pebble, a 
blade of grass, and a fly, or other insect, and make a list 
of the things in which they differ. 

2. Place some sand and some wheat grains in a box 
where they will be free from moisture and sunlight. Put 
some grains of sand and some grains of wheat in soil which 
you have placed in a box of convenient size, and put in a 
warm place where they will have plenty of sunlight. Keep 
them well watered. Examine them every day, and note 
any changes that take place. How do you account for the 
difference in what takes place? Why do they each remain 
unchanged in the first case ? What have you learned that is 
essential to the life and growth of the wheat grain? What 
would happen if you should place a grasshopper or a fly in 
a box where it could get only soil, water, air, and sun- 
light ? Why ? What do the grasshopper and the fly live 
on i What does this teach ? 

3. Plant some seeds of the bunch bean or dwarf pea, 
and note carefully what takes place. Are all the parts 
alike ? Can you think why the parts are not alike ? why 
the leaf differs from the stem, or the roots, or the flower ? 

4. Get some snail's eggs or frog's eggs, and put them 
in a vessel of water in a warm place. Carefully watch 
them from time to time. What do you learn from these 
observations ? 

A body which behaves like the grain of sand is called a 
mineral ; one like the grain of wheat or the bean, a plant ; 
and one like the fly, an animal. Make a list of the things 
you have observed of each. 



2 EXPERIMENTS AND DEMONSTRATIONS. 

Query 1. Upon what are plants dependent for their life 
and growth ? the animals ? 

Query 2. What would happen to plants were there no 
soil ? To animals if there were no plants ? Why do we 
need to study animals? 

5. Prepare for dissection a rat or a rabbit as directed 
in the Appendix. Notice the general plan. If you should 
divide the body into halves (right and left) on a middle 
{median) line drawn from above downward, how would 
the two parts compare ? What name shall we give to the 
front surface of the body ? to the rear surface ? Into what 
parts is the front surface divided ? How is the rear surface 
divided? Examine diagram, Fig. 1. 

6. Examine transverse section of a tadpole or a sala- 
mander, prepared as directed in the Appendix. Notice 
(1) a large cavity, (2) a small cavity. How do they differ 
in their boundaries? The larger cavity is called the ven- 
tral, or hcemal (Eig. 2) ; the smaller, the neural, or dorsal, 
cavity. 

7. Begin at the chin, and divide on a median line the 
anterior surface of the specimen of Experiment 5, carry- 
ing the line to the upper part of the pelvis. Examine the 
contents of the cavities thus exposed. Into how many 
parts is the cavity divided, and by what kind of mem- 
brane? By means of the diagram (Eigs. 5 and 6) learn 
the names of the parts {organs) contained in the cavities. 
Notice form, size, and relation of each. Make an outline 
drawing of the cavities and their contents. 

8. Remove the skin from the back part of the skull 
and the back. Saw into the skull-cavity, or remove the 
bone by means of the bone forceps so as to expose the 
contents of the cavity. Continue the line down the back, 
cutting away the bones with bone forceps, to near the end 
of the backbone (vertebral column). Determine the name 
of the organs contained in these cavities. (See Eig. 3.) 

9. Remove a small portion of the skin from the leg or 
soles of the rabbit. (It is best, however, to shave off the 
hair from the part from which you take the portion of skin 
before removing it.) Elarden the specimen by placing 
it in a, two-per-cent solution of chromic acid for a week. 
Then transfer to sixty- and then eighty-per-cent alcohol. 
Make a vertical section, and stain in picrocarmine, mount 



EXPERIMENTS AND DEMONSTRATIONS. 3 

section in glycerin, and observe that it is made up of two 
portions, the outer one of which is composed of little 
bodies (cells) more or less rounded, the inner of fibrous 
material. 

10. Take out some of the flesh (muscular tissue), and 
examine the little fibers first with a two-thirds and then 
with a one-fifth objective. 

11. Examine a prepared section of the posterior gan- 
glion of the spinal nerve of a cat ; also a section of the spinal 
cord. Xotice the numerous little bodies which make up the 
greater part of the substance of these bodies. 

12. Examine a vertical section of the tongue of a cat. 
Xotice the structure of the membrane (mucous membrane) 
which covers it. Observe that in Experiments 7, 8, 9, 10, 
and 11 we have examined organs whose essential struc- 
ture is cellular. We class such organs in the Cellular Sys- 
tem. See if you can determine what organs belong to this 
system. 

13. Take the specimen used in Experiment 5. Place 
the animal upon its back. Xotice the tube-like body (trachea) 
in front, in the neck; trace it to some of its smaller 
branches. Of what do the lungs seem to be chiefly com- 
posed ? 

Xotice what kind of vessels come to it and go from 
it. Do you know what these tubes are called % Trace the 
larger ones for some distance. What do you learn? 

Remove the lungs and heart. Examine the tube 
(esophagus) lying back of them. Trace it in its course 
through the body. Xotice that while it is expanded in 
some parts and contracted in others it is in reality a single 
long tube. 

11. Examine a prepared section of the skin with a one- 
fourth objective. Xotice the little knot of tubes (sweat 
glands) originating in the lower part of the skin and pass- 
ing upward and opening on its surface. 

What do you think would be a good name for the system 
which includes organs whose essential structure is that 
of tubes or modified tubes ? See if you can find other 
organs than those we have examined which belong to this 
system. 

15. Remove the skin of the cat or rabbit you have been 
studying. Xotice how it is attached to the body. How 



4 EXPERIMENTS AND DEMONSTRATIONS. 

is the flesh (muscles) bound together? What is it that 
gives firmness and support to the limbs ? Examine the 
organs in the abdominal cavity, and notice how they are 
bound together. Why are they so carefully bound to- 
gether ? What seems to be the use of these structures ? To 
this system we give the name of the Skeletal System. It 
may seem to you that we have grouped together things 
which are very much unlike; our later study, however, 
will show us they are very closely related in structure and 
origin. 

16. Examine the teeth, tongue, and muscles of the 
face, jaws, and salivary glands. How do they compare 
in form and structure ? Can you think of anything they 
work together to perform ? Do you know what we call such 
a group of organs ? See if you can find other groups of 
organs, differing in structure and form, which act together 
to do a common work. Such a group of organs is called an 
apparatus. Examine Eig. 7, and see how your observations 
agree with the statements made there. 



THE HUMAN BODY. 

INTRODUCTION. 

Its Relation to Other Bodies. — We have learned that 
the separate portions of matter are called bodies ; as a 
pebble, an apple, and a cat. While there are many millions 
of these, differing in size, form, properties, and actions, yet 
we may put them in one of two groups. 

In the first group we class those that are of simple 
composition and structure; that do not. increase in size 
except by addition of particles to their surface; that do 
not require food; that do not have life. Such bodies are 
called minerals. 

In the second group are included those which are of 
a complex structure and composition; increase in size 
(grow) by taking food; have a regular cycle of existence, 
i. e., are brought into existence (birth) ; attain a certain 
size and development (growth) ; bring forth forms like 
themselves (reproduction); decline; die. These axe living 
bodies, or organized bodies. To the first group belong the 
soil, rocks, the earth, air, and water; to the second, the 
various plants, animals, and man. 

While the minerals, plants, and animals are appar- 
ently so different and unrelated, they are, in fact, very 
dependent, — the plant on the mineral, the animal on the 
plant and mineral. How are plants, animals, and minerals 
dependent ? 

The human body is the greatest and most wonderful of 
living forms, yet it is related in many ways to the lower 
forms, and the study of these aids us very much in under- 
standing our own bodies. In fact, most of the principles of 
life action and function of organs have been learned by ex- 
periment on lower animals. 

The animals which have been of most service to us in 
this way are the amoeba, the frog, the cat, and the dog. 

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THE HUMAN BODY. 7 

The human body is the house in which we live — the 
temple of the soul. The care we give it will greatly affect 
our health, our happiness, and our usefulness. How impor- 
tant for us to know its structure and its workings, that we 
may so care for and use this wonderful body of ours that 
life may be made the most to ourselves and to others ! 

Regions of the Body. — That we may better understand 
its parts, let us first view the body as a whole. We may take 
for examination either a rabbit or a manikin. 

The human body presents for study a front, or ante- 
rior, and a back, or posterior, surface. Its parts are the 
head, trunk, and extremities. Study Fig. 1. The principal 
regions of the anterior surface are the head, neck (cervical), 
chest (thoracic), and abdomen; of the posterior surface 
they are the head (cephalic), neck (cervical), back (dorsal), 
loins (lumbar), sacral, and gluteal. Study Fig. 1. The 
extremities include the upper and lower limbs. The regions 
of the upper extremity are the shoulder, arm (brachial), 
forearm (cubital), and hand. Those of the lower extremities 
are the thigh (femoral), leg, and foot. 

The names which physicians and scientists give the 
regions of the body may be learned by examining Fig. 1. 

In order to learn the internal structure of bodies, sci- 
entists ffenerallv make two sections: one, from above down- 
ward, called a longitudinal section; one crosswise, from 
before backward; a transverse section of the human body 
in the dorsal regions (Fig. 3) ; a longitudinal on the median 
line of the body; i. e., a line which would divide the body 
into two equal parts, a right and a left. From these sections 
we learn that the body consists of two tubes, one the posterior 
(the dorsal, or neural, Fig. 4), the other the anterior (the 
ventral, or hcemal, Fig? 4). 

Xotice that the dorsal cavity is surrounded by bone, 
the ventral only partly so. Can you give any reason for 
this difference in structure ? Xotice also that the dorsal 
is one continuous cavity; that the ventral is divided by a 
muscular partition (the diaphragm) into two portions, the 



8 



THE HUMAN BODY. 




upper or thoracic cavity, and the lower or abdominal cav- 
ity (Fig. 3). . 

From the specimen you have for dissection, or from 
the manikin, determine the organs contained in these cavi- 
ties. They may also be learned by a study of Figs. 3, 5. 

and 6. From these we 
learn that in the neural 
cavity is contained the 
central nervous system; 
in the upper portion, the 
cranial cavity, the brain; 
in the remainder of this 
cavity, formed by the 
spinal canal of the back- 
bone, or vertebral col- 
umn, is contained the 
spinal cord with its ter- 

Fig. 2.- transverse Section of minal nerves ; in the ven- 

Necturus. 

A Dorsal cavity formed by the vertebra. tral cavit ^ in the ll PP er 

or thoracic portion, the 
lungs, trachea, bronchial 
tubes, heart; back of these, the esophagus, great blood vessels, 
aorta, venae cava?, thoracic duct, chain of sympathetic gan- 
glia; and in the lower portion, the abdominal cavity, the 
stomach, liver, small intestines, large intestines; back of 
these, the pancreas, spleen, chyle cistern (receptaculum 
chyli), great blood vessels, kidneys, bladder, and chain of 
sympathetic ganglia. 

Make an outline drawing of these cavities and their con- 
tents, either from the specimen you have dissected or from 
the manikin, or, if you do not have these, from Figs. 5 and 
6. Carefully note the relation of these parts. 

Organs. — A part of a living body having a separate 
work to perform, the performance of which is concerned 
with the well-being or use of the body, is called an organ; 
as, the hand, the eye, a bone, or a muscle. 

An organ may be very simple in structure, as a 



2. Spinal cord. 3. Ventral cavity. 4. Ali- 
mentary canal. 5. Liver. 6. Muscles of the 
body wall. 7. The skin. (Brinckley, O. W. B.) 





Fig. 4.— Transverse Section of 
Human Body (very diagrammatic). 

L Dorsal cavity. 2. Spinal cord. 
3. Ventral cavity. 4. Alimentary 
tract. 5. Body wall. 



Fig. 3.— Section of Human Body on 
Median Line (diagrammatic). 

1. Dorsal cavity. 2. Cranial cavity, 
containingthe brain. '6. Vertebral canal, 
containing spinal cord. 4. Ventral cavity. 
5. Thoracic cavity. 6. Abdominal cavity, 
7. Alimentary tract. 8. Respiratory tract. 
9. Heart. 10. Diaphragm. 11. Liver. 
12. Pancreas. 13. Stomach and intestines. 
14. Urinary tract. 



I'LATE 1. 



SYSTEMS. 9 

muscle, or very complex, consisting of simpler organs, as 
the hand. 

The work which an organ performs is called its function ; 
e. g., the function of the eye is vision; of a muscle, contrac- 
tion to produce motion. 

Can the following parts properly he termed organs : the 
nose, the ear, the tongue, the arm, a hone, a nerve, a hair, 
and the skin ? Give reasons for your answer. 

Systems of the Body. — When organs have essentially 
the same structure, and work together to perform a common 
work or function, the group of organs is called a system; 
thus the muscles of the hody form the Muscular System, 
those of the heart, arteries, capillaries, and veins form the 
circulatory system. 

Let us now take a closer view of the hody. If we 
should examine a small portion of the skin (Fig. 142), 
some nerve tissue (Fig. 83), and a portion of a muscle 
(Fig. 49) under the microscope, we should find the prin- 
cipal element of their structure to he a very small hody 
having a more or less regular shape, called a cell. Those 
organs whose essential structure is the cell belong to the 
Cellular System. 

This system is divided into three smaller ones: 1, The 
covering (the shin) and the lining (mucous membrane) of 
the hody, forming the Muco-Dermal System; 2, the flesh 
of the body (muscles), whose chief function is to produce 
motion, forms the Muscular System; 3, the brain and 
spinal cord, with the nerves that go from them, with the 
sympathetic nerves, ganglia, and plexus, which make up the 
Nervous System (Fig. 7). 

Throughout the body are numerous organs whose essen- 
tial structure is that of single tubes, or sacs, or of a series 
of tubes; as the arteries and veins, the windpipe (trachea). 
Such structures belong to the Tubular System (Fig. 7). 

Beginning at the mouth, we notice that it leads into an 
expansion (the pharynx), which in turn leads into a mus- 
cular tube (the esophagus) (Fig. 110), which expands (the 



10 THE HUMAN BODY. 

stomach), then contracts (the intestines), and then becomes 
enlarged again (the larger intestines). As this is the tube 
along which food is digested, it is called the Alimentary 
System (alimentary canal). Before reaching the mnscular 
tnbe we find an opening (the glottis) leading into a funnel- 
shaped box (the larynx), surmounting a tube (the trachea), 
which becomes very much branched (the bronchi), so as to 
make a complicated system of tubes, forming the greater 
part of the lungs. As this is the tube by which we breathe, 
it is called the Respiratory System. Could we trace one 
of the little blood vessels in its course, it would be seen 
to join with others, and these with still larger ones, until 
they form a great trunk extending to the heart, and here 
would be found various large tubes going to and from the 
heart. These, with the heart and the tubes which carry 
the lymph, since they are the means by which the materials 
are carried to and from different parts of the body, are 
called the Circulatory System. 

In various parts of the body are found bundles, or a 
network of tubes, whose purpose is to form materials, fluids, 
and solids for the use of the body ; these form the Secretory 
System. For the organs which belong, to this group, see 
Fig. 7. 

There are also collections of tubes, in some cases very 
complicated, whose purpose is to remove waste materials 
from the body ; these form the Excretory System. 

The Tubular System, therefore, may be divided into: 
1, The one for the digestion of food — the Alimentary 
System ; 2, the one by which we breathe — the Respira- 
tory System; 3, the one by which material is carried to 
and from various parts of the body — the Circulatory Sys- 
tem; 4, those making material for use of the body — the 
Secretory System; 5, those for the removal of waste prod- 
ucts — the Excretory System. 

For the relation of the systems to the organs which they 
contain, see Figs. 5 and 6. 

As we have seen, the muscles, nerves, and delicate organs 



p <w x 8 £ OQ O 

P«T?5t' C go 




©■o =»§ 5. 




c?3 ^ 



12 THE HUMAN BODY. 

need protection and support, and without such support our 
bodies would be like that of the jellyfish, and as helpless as 
it would be out of the water. 

Again, long tubes like the intestines, if put into the 
abdominal cavity without support, would be in constant 
danger of entanglement; we therefore find them securely 
bound together by a delicate membrane (the mesentery). 
There are other organs which must be bound to their places. 
The contraction of a muscle would amount to but little, and 
movement of the body would be almost impossible, if the 
muscles did not have some firm structure upon which to 
act, as the bones. This investing, supporting, protecting 
system forms the Skeletal System. To this system belong 
connective tissue proper, ligaments, tendons, cartilage, and 
the bones. 

Apparatus. — Organs which are very unlike in struc- 
ture, which work together to produce a common work (as 
the muscles, bones, and nerves, to produce motion; the 
teeth, tongue, salivary glands, liver, and alimentary canal, 
to effect the preparation of the food for absorption), form 
an apparatus. 

The more important kinds of apparatus of the body 
are those of vision, hearing, taste, smell, motion, respira- 
tion, digestion, and circulation. We shall learn later in 
our study the organs of which these apparatus are com- 
posed. 



SYSTEMS. 



13 



Fig. 7. — Diagram of the Systems of the Human Body. 



Systems.— 
Groups of 
organs es- 
sentially 
alike in 
structure. 



Cellular.— The 
cell the es- 
sential ele- 
ment of 
structure. 



Muco-dermal. 



Skin and appendages. 
Mucous membrane. 



Muscular. -J Muscles. 



Nervous. 



r 



Tubular. — 
Tissues ar- 
ranged in 
the form of 
tubes or 



Digestive. 



Respiratory. 



Circulatory. 



Secretory. 



Excretory. 



Skeletal. — More or less of tis- 
sues giving protection, form, 
and support to organs. 



f Brain. 

Spinal cord. 

Cranial and spinal 
nerves. 

Sympathetic nerves. 
n Ganglia and plexuB. 

r Mouth. 
I Pharynx. 

(Esophagus. 
Stomach. 
Intestines. 

f Nasal passages. 
I Pharynx. 
] Larynx. 

Trachea. 

Bronchi. 
w Lungs. 

f Heart. 

Arteries. 

Capillaries. 

Veins. 
\ Lymphatic capillaries. 

Lymphatic veins. 

Lacteals. 

Thoracic duct. 
(^Lymphatic glands. 

f Salivary glands. 

Gastric glands. 
J Intestinal glands. 
' Liver. 

Pancreas. 
| Lachrymal glands. 
(^Sebaceous glands. 

Kidneys. 
Lungs 
Sweat glands. 

f Connective tissue. 
| Tendons. 
<! Ligaments. 

Cartilage. 
1 Bone. 



CHAPTEK II. 

EXPERIMENTS. 
MICROSCOPIC STRUCTURE OF THE BODY. 

1. Prepare a specimen of the skin as directed in 
Experiment 9. Use a one-fifth objective for examination 
of the object. What do yon find to be the structure of the 
outer layers ? Make a drawing of the cell layers, carefully 
noting their structure. 

2. Make a vertical section of the tongue, and harden 
and prepare as directed for the skin as given in experiment. 
Carefully note the covering structure, and compare with the 
section of the skin. Examine in a similar way the mucous 
membrane of the throat. 

3. Take a piece of the membrane which holds the 
intestines together (the mesentery), and immerse in a quar- 
ter- or a half-per-cent solution of silver nitrate for a few 
minutes, then wash in water. Expose the membrane to the 
sunlight until it becomes brown; now spread it out upon a 
glass slide, and place it for a short time in a very dilute 
solution of ammonia carmine, adding a few drops of acetic 
acid; wash in slightly acidulated water. Acid a drop of 
glycerin to the slide, and put on a cover glass. Examine 
with the microscope, and make drawing of whatever you see. 
In what respect do the tissues you have examined seem to 
be alike? 

These tissues are called epithelial tissues. Examine the 
interior of various organs to see if they are lined with 
epithelium. Make a list of the organs in which you find 
epithelial tissue ; also notice how the form and arrangement 
of the cells differ in the different organs and tissues. 

4. Obtain from the butcher a portion of the large 
tendon or ligament (ligamentum nuchoe) which holds the 
head of the ox erect. Note the structure of the ligament. 
(1) Tease out in water a small portion; i. e., carefully tear 
it into small threads by moving the teasers the long way 
of the tendon. 

14 



EXPERIMENTS. 15 

Of what kind of libers is it composed ? Are they elastic ? 
How do yon know? Make a drawing of your specimen. 
(2) Add to the specimen a three-per-cent solution of acetic 
acid. What change takes place? 

5. Get a mouse, and kill it with chloroform as directed 
in the Appendix. (1) By means of the forceps pull off a 
portion of its tail, and, keeping in position one end with a 
needle, separate as completely as you can the fibers. Dur- 
ing the process of teasing, the fibers should be kept moist 
with a normal salt solution. See Appendix. Add a drop 
of normal salt solution, and put on a cover glass. Examine 
with the microscope. Observe the bundles of fibrillar. 
Make a drawing. (2) Now add a three-per-cent solution of 
acetic acid. What change takes place? The fibers which 
now remain are elastic fibers. 

6. (1) Make a very thin section of the head of the 
humerus or femur of a young animal. Mount in a nor- 
mal salt solution (six-tenths-per-cent of common salt), and 
examine with a high power. Note, (a) the apparently 
structureless part (the matrix) in which are distributed, at 
somewhat irregular intervals, cells (cartilage cells or cor- 
puscles) ; (b) the shape of each corpuscle, with its promi- 
nent center (nucleus) ; (c) that most of the cells fill up the 
cavities in which they lie; (d) the nature of the matrix, and 
its proportion to the number of cells. (2) Wash the piece 
with a one-per-cent solution of acetic acid. Note the changes 
which take place as washing proceeds: (a) changes in the 
nucleus; (b) changes in the cell's substance; (c) the space 
formed by the shrinking of the cell. (3) Place a small 
piece in a five-per-cent solution of gold chloride for about 
a half hour, or until it is of a light yellow color, then 
wash well with water, and place in a vessel containing 
water slightly acidulated with acetic acid; leave it exposed 
to the light. 

When it has become of a red purple color (which will 
require in most cases one or two days), mount in glycerin. 
Note the changes. Make a drawing. 

7. Take a thin portion of a tadpole's tail, and harden 
by placing in a two-per-cent solution of chromic acid. When 
sufficiently hardened, gently break up a piece of glycerin. 
Notice the hexagonal cells composing the outer layer 
(epidermis) of the skin. When these have been broken 



15 EXPERIMENTS. 

away from the layer, in which are imbedded many blood 
vessels, a number of stellate cells may be seen. Note the 
layer of dark stellate cells (connective tissue corpuscles). 
Notice carefully their structure and relation. 

8. Cut out a small piece of the mesentery from a part 
containing little fat. Spread it out on a slide, and mount 
it in a normal salt solution. Examine: (1) Put under a 
low power, and notice the groups of highly refractory cells. 
(2) Place under high power, and notice relative size and 
structure of the fat-cells. In what do they seem to be im- 
bedded? Have the cells a nucleus? (3) A specimen that 
has its blood vessels injected. Note carefully the arrange- 
ment of the blood vessels. In what tissues and organs do 
you find fat ? See if you can determine how fat tissues 
are formed. Does it seem to have any relation to connective 
tissues? See if you can discover the use of fat. Write a 
description of the tissue observed. Make a classification 
of tissues observed, as to essential structure. 

THE MICROSCOPIC STRUCTURE OF THE BODY. TEXT. 

If we should carefully dissect any of the organs of the 
body, as for instance a muscle, we should find that it is 
made up of a number of simpler parts or membranes. These 
simpler structures which go to make up the organ are called 
tissues. 

By dissecting out the various organs of the body, and 
comparing their structure by means of the microscope, we 
can learn more fully of their structure and the relation of 
the tissues. The study of the microscopic structure of organs 
and tissue has become a great science, and is called histology; 
and when we speak of the histology of a tissue we have refer- 
ence to its microscopic structure and appearance. This science 
has revealed to us many wonderful truths, and made possible 
many things which could not have been known without it. 

From a histological examination we are able to classify 
the tissues into the following groups : — 

I. Those whose essential structure is one or more layers 
of cells resting upon a delicate, almost structureless layer — 
Epithelial tissue (Fig. 8). 

II. Those whose property is to contract and relax — 
Muscular tissue, or contractile tissue (Fig. 14). 



THE MICROSCOPIC STRUCTURE OF THE BODY. 



17 




Fig. 




8.— Epithelial 
Tissue 
Epithelium of the 
bladder showing the 
nature of transitional 
epithelium. Notice 
difference in shape of 
the cells. 



III. Those which can receive impressions, and send 
stimuli — Sensory or nervous tissue (Fig. 85). 

IV. Those made up of fibers and cells, and whose chief 
function is to support or bind parts together — Connective 
tissue (Figs. 20, 21, 22, 23). 

V. Those composed of liquid, in which float small bodies 
(corpuscles), and whose function is to carry material to 
and from the various parts of the body — Nutritive tissue, 
the Blood, and the Lymph (Fig. 137). 

1. Epithelial Tissue. — Distribution. — 
Epithelial tissue forms (1) the outer layer 
of the skin, where it is known as the 
epidermis; (2) the covering of the mucous 
membrane, i. e., those membranes which 
line the passages and cavities of the 
body which communicate with the ex- 
terior, as the air passages, the lungs, ali- 
mentary canal, and also ducts and tubes 

o pen- 
in g in- 
to these 
cavities; (3) the ter- 
minal parts of the 
organs of special 
sense, as the rods and 
cones of the retina, and 
the auditory hairs; (4) 
inner surface of serous 
membranes; i. e., the 
membranes lining 
closed sacs, as in the 
thorax (pleura), abdo- 
men (peritoneum), and 
of the heart (pericar- 
dium) ; (5) inner sur- 

Fig. 9.- Ciliated Epithelium. face of the heart, blood 

From section of bronchus, a. Ciliated col- „ nnnn -\„ „_j i_ ,_i ni .- 
umnar cells, b. Mucous membrane, c. Bundle ^ eSbdS, and lymphatics J 
of unstriped muscular fibers, d. Submucous ( n\ j 11T . pi , linino' rvf* flip 
membrane showing cross sections of gland v./ 11U1C1 Ullill & UJ - VL1Kj 
tubes, e. Portion of cartilaginous tubes, f. vpntrip]p« n-f -rhp Krain 
Section of artery on left, and on right a vein. v emiK.ie& OI me Uidm 
g. Section of nerve fibers, h. Section of gan- and the Central canal of 
glion. (After Sanderson.) , . ., 

the spinal cord. 
Structure. — Epithelial tissue consists of cells placed 
side by side, held together by a small amount of cementing 

2 



18 



THE MICROSCOPIC STRUCTURE OF THE BODY. 




Fig. 10.— Columnar Epithelium. 

Mucous membrane of villus of Intestine 
of Necturus. (Brinckley, O. W. B.) 



substance. Epithelial cells consist of protoplasm and a 
nucleus; they multiply by indirect division (karyohinesis). 
As they vary in their functions, — as protecting, secreting, 
and receiving sense impressions, — they present a correspond- 
ing variety in form, structure, and size. As to their arrange- 
ment, they may be strati- 
fied, forming several lay- 
ers, as in Fig. 9, or simply 
composed of a single layer. 
In form they may be 
squamous or flat (Fig. 8), 
columnar or cylindrical 
(Fig. 10), or cubical. No 
blood vessels pass into 
epithelial tissue; they are 
nourished by imbibition 
of the plasma from the 
tissues near them. In 
many parts, however, 
nerve fibrils exist among 
the epithelial cells. 

The more important varieties of epithelial tissues are : — 

1. Stratified Epithelium — This form of epithelium 

forms the external surface of the 

body, or the epidermis; it also 

^S^^SPSSJBWPIfts lines the cavity of the mouth, 

- 1 '^-?* i " . .-A*,: \4V ^<mk pharynx, esophagus, and the 

anterior surface of the cornea. 

2., Transitional Epithelium. — 
This variety is quite widely 
distributed. A squamous variety 
lines the bladder and ureters. 
It consists of three or four layers 
of cells having prominent nuclei. 
The most superficial layer consists of somewhat flattened 
cells, each of which overlies two or three pear-shaped cells of 
the second layer; a third layer fills up the spaces in the 
second, as shown in Fig. 8. A columnar variety, consisting 
of three or four layers of cells, forms the lining of the 
larynx, trachea, and large bronchi. 

3. Simple Squamous or Pavement Epithelium.— Th i s is 




Fig. 11. — Pavement Epithelium 

fbom the Mouth of a Child. 

(Sanderson.) 



EPITHELIAL TISSUE. 



19 



made up of a single layer of flattened, many-sided cells, 
fitting edge to edge, as in Fig. 11. It lines the air cells of 
the lungs, part of the looped tubules of the kidneys, the 
inner surface of the iris and choroid, and the free surface 

of serous rnem- ^ . _^ 

branes, as the I 
pleura, peri- 
toneum, pericar- 
d i u m , and the 
arachnoid m e m - 
brane, and the in- 
terior of the heart, 
blood vessels, and 
lymphatics. 

4. Simple Col- 
umnar Epithelium. 
— Columnar epi- 
thelium consists of 
prismatic or cylin- 
drical cells set 
upright, and 
generally of 
but one layer. The 
cells are often 
very irregular, 
due to mutual 
compression and 
the presence of 
lymphoid or wan- 
der cells. In 
many parts of the 
mucous membrane 
the columnar cells 
undergo modifica- 
tion of shape due 
to their distention 
to form the secre- 
tion of mucin, the 
chief constituent 




Fig. 12.— Prickle Cells. (From human skin.) 

1. Prickle Cells. 2. Epidermis, a. Layer of horn 
cells, b. Stratum lucidum. c. Granular layer 
Stratum intermedium. e. Rete mucosum. 



I 



of mucus ; becoming flask-shaped, they are called goblet cells 
(Fig. 26). They finally rupture their contents, forming 
mucus. 



20 THE MICROSCOPIC STRUCTURE OF THE BODY. 

5. Ciliated Epithelium. — The cells of this tissue are 
usually columnar, having at their free ends hair-like 
processes called cilia (Fig. 9). During life, and in 
many cases for a short time after removal from the 
body, they exhibit a rapid, whip-like movement, the surface 
moving to and fro like a field of grain swayed by the wind. 
The cilia bend swiftly in one direction, and then return to 
an upright position more slowly, thus setting in motion in a 
definite direction the fluid which bathes them. It is in this 
way the mucus is moved along the bronchial tubes and 
trachea to the pharynx. Ciliated cells line the nose, the upper 
half of the pharynx, the Eustachian tubes, the lower part of 
the larynx except over the vocal cords, the trachea and bron- 
chial tubes, the ventricles of the brain, and the central canal 
of the spinal cord. 

6. Sensory Epithelium. — This is a curious modification 
of cells, found in connection with the termination of certain 
sensory nerves to form receptive end-organs for different 
kinds of vibrations, as the rods and cones of the retina (Fig. 

159), and the auditory 
hair-cells (Fig. 170). We 
shall study these more at 
length when we consider 
the different senses. 

Function of Epithelium. 
— With the exception of 
the sensory epithelium* the 
epithelium is either protec- 
tive or secretive in its func- 
tions. The epithelium 
forming the epidermis, the 
Fig 13.— Cross Section of a Skeletal lining 01 the air passages, 

MusCLE - . and the eyelids, is mainly 

(Section of one of the flexors of the d , " 

foot of ox.) 1. Epimysium. 2. Perimysi- protective, while that 01 
um. 3. Bundle. 4. Endomysium. 5. Fas- r 7 

cicuius of fibers. (Brinckiey, s. d. o.) the salivary glands, the 
gastric and intestinal glands, of the liver, of the pancreas, 
and of the sweat glands is secretive. 

Ciliated epithelium, in addition to being protective, aids 
by its movements in propelling fluids and small particles 
from the body. 




CONTRACTILE TISSUE. 



21 



Beneath the epithelium of many tissues is found a homo- 
geneous membrane, the basement membrane. That of most 
mucous membranes and secreting glands, however, consists 
of a very thin layer of flattened cells, a variety of connective 
tissue. 

II. Contractile or Muscular Tissue. — This is the tissue 
that makes up what is called the flesh. It is also found as 




1. Striated fiber. 2. Nucleus. 3. Striae. 4. A fibrilla. 5. Muscle 
fibers from tongue of cow. (Brinckley, G. W. B.) 



one of the coats of the alimentary canal, in the middle coat 
of the arteries and veins, makes up the greater part of the 
heart, and is found in some other parts of the body. 

The muscles attached to the bones, and concerned with 
the movements of the skeleton, are called skeletal muscles. 
Those of the blood vessels and alimentary canal are called 
involuntary muscles. 



22 



THE MICROSCOPIC STRUCTURE OF THE BODY. 



Skeletal Muscles. — To the eye the skeletal muscles have 
the appearance of being made up of numerous bundles (Fig. 
13) of very small bundles, all bound together by connective 
tissue. The investing sheath of the muscle is called the 
epimysium ; that which divides the muscle into bundles, the 
perimysium. The smallest bundles, microscopic in size, are 
called fasciculi ; each fasciculus is seen to be made up of 
very fine threads or fibers (Fig. 13). While they appear to 
be a continuous thread, they are made up of small elongated 
cells placed end to end, being gi ¥ of an inch thick and many 
times longer. The fibers are usually over an inch long, and 
are covered with a sheath called the sarcolemma. They ap- 
pear to have fine cross-markings, or striae, and numerous 
nuclei lying close to the sarcolemma. 

When specially treated, or after death of the muscle, 
the fiber presents fine longitudinal markings called fibrillse. 

Under very high powers 
the muscle appears much 
more complex than given 
above, but it would take us 
too far to consider it here. 
Besides binding and 
connecting the various 
parts of the muscle, the 
connective tissue (are- 
olar) serves to conduct and support the blood vessels and 
nerves in their ramifications in the muscles. 

Unstriped Muscle.— When we examine the muscles 
which go to make the muscular coats of the alimentary canal 
and blood vessels, we find them quite different in structure. 
These muscles are made up of bundles bound together by 
connective tissue. 

The fibers are composed of spindle-shaped cells, some- 
what flattened, having a length of T J ¥ inch and a breadth 
of one eighth of the length, or about ^Vo of an inch. 

They have a prominent oval-shaped nucleus with well- 
marked network and one or more nucleoli. The cell sub- 




Fig. 15.— Unstriped Muscle Cells. 
I. Nucleus. 2. Longitudinal striae. 
Arrangement of cells. 



CONTRACTILE TISSUE. 



23 



stance presents a longitudinal striatum, but no transverse 
marking. Each cell seems to have a delicate sheath; the 
cells are held together in the fibers by a small amount of 
cement substance. 

As in the skeletal muscle the blood vessels and nerves 
find their way to the fibers by means of the connective 
tissue. This variety of muscular tissue is called plain or 
unstriped muscular tissue (Fig. 15). Unstriped muscle is 
found in the muscular coat of the alimentary canal below 
the middle of the esophagus, in the trachea and bronchi, in 
the middle coat of the arteries, in the veins and larger 
lymphatics, in the blad- iffifonrnTrVrr^) nsrm C\ 

der and ureters, and in 
the ducts of glands. 

Heart Muscl e.— 
The heart muscle fibers 
resemble those of the 
skeletal muscle in hav- 
ing transverse stria?, but 
they differ in many 
other respects. The 
fibers often give off 
branches, as shown in 
Fig. 16. The cells are 
more nearly square, 
have a prominent nu- 
cleus placed near the Fig. 16.— heart muscle. 
center of the cell, and L Nucleus ' 2 ' B m r ^ c n h g S. celL 3 ' AnaSt °" 
are without a sarcolemma. The different muscular tissues 
differ also in function as well as in structure. The striped 
varieties, except heart muscles, are under the control of the 
will, and are called voluntary muscles. The unstriped and 
heart muscles act independently of the will, and are called 
involuntary muscles. 

In action the striped, or voluntary, muscle is the most 
rapid, the heart muscle the next, and the unstriped muscle 
the slowest. 




24 THE MICROSCOPIC STRUCTURE OF THE BODY. 

III. Nervous Tissue. — This is the tissue which makes 
up the brain, spinal cord, and nerves. The principal varie- 
ties are the gray nerve substance, composed of cells, and the 
white nerve substance, whose chief element is fibers. We 
shall learn more about these when we study the nervous 
system. 

IV. Connective Tissue. — Definition. — The term " con- 
nective tissue " includes a number of tissues, which, while 
they appear to differ widely, are grouped together, owing 
to their common function and origin, and to their histological 
and chemical similarities. 

Origin and Structure. — They have a common origin, 
being all derived from the mesoblast. Histologically they 
are related, in that they have, in common, three microscopic 
elements : a ground substance or matrix, cells, and fibers, the 
proportion of which varies in the different forms of con- 
nective tissue. 

All varieties of this tissue, which contain white fibers, 
yield gelatin on boiling. 

In some cases these tissues may replace each other or 
merge into one another, as cartilage into bone or areolar 
tissue into adipose. There are three principal varieties of 
connective tissue, viz. : — 

A. Connective Tissue proper, of which there are six 
varieties : — 

1. Areolar Tissue. — This tissue has more or less open 
texture, and appears to the naked eye to consist of fine, 
transparent threads and films crossing in various directions, 
and leaving, especially when stretched, open spaces, or 
areolce, between them. 

Under the microscope the transparent threads are seen to 
be made up of wavy bundles of very fine parallel fibers 
(white fibers), going in various directions, with a single 
branching fiber of another kind (elastic fibers). 

In addition to these fibers, various forms of connective 
tissue cells may be found: (1) flattened connective tissue 



CONNECTIVE TISSUE. 



25 



corpuscles, (2) plasma cells, (3) granular cells. Besides 
these fixed forms, are cells (wandering cells) like those of 
the white corpuscles of the blood and lymph. Cementing 
the white fibers together, and forming the matrix, or basis, 
of the tissue, is a clear homogeneous material containing 
mucin, called the ground 
substance. 

Distributio n . — 
Areolar tissue is the most 
widely distributed of the 
connective tissues. It is 
found beneath the skin 
and mucous membrane, 
forms sheaths and parti- 
tions, tissues of muscles 
and of various organs, 
and binds various parts 2,-f— 
and organs together. It 
forms a continuous net- 
w o r k throughout the 
body, investing, support- E^ 

ing, and binding its vari- 
ous parts together. 

2. White Fibrous Tis- 
sue. — Structure. — This 

tissue consists essentially Fig. 17.- White Fibrous Tissue (Cornea). 

n-F lvi-mrlloe n-P Whi+o h White fibers. 2. Fusiform cells. 3. 
ui uunuies oi Vv mie structure of cornea, a. Epithelial layer, b. 
■fihpvQ flip ntlipr ol^memta Outer elastic layer, c. White fibrous layer. 
noeiS, me Other elements, d> substantia propia (proper substance of the 
_ .£___ „~n„ n ^A ^™,-^+ cornea), e. Posterior elastic layer, /. Inner 
a lew cells and cement- epithelial (endothelial) layer. 

iug substances, being comparatively unimportant. The com- 
pact varieties have a shining pearly appearance, are very 
strong and pliant, but quite inelastic. 

Under the microscope what appears to be fibers is made 
up of many very fine transparent fibers from -^i^ to ^-sioo 
of an inch thick. These fibers do not occur singly, but are 
cemented into a bundle by a small quantity of the mucin 




26 



THE MICROSCOPIC STRUCTURE OF THE BODY. 



ground substance. While the fibers are transparent by 
transmitted light, in mass they appear white. The fibers 
run principally in one direction, and do not interlace or 
branch (Fig. 17). 

Distribution. — This tissue forms the chief part of ten- 
dons and ligaments, is found in the true skin and the denser 
f ascise, binding down the muscles. 

3. Yellow Elastic Tissue. — Structure. — In this tissue 
the elastic fibers predominate. The yellow fibers are dis- 
tinguished from the white by their sharper outline, yellow 
color, and their branching or anastomosing, and forming a 

network. They curl up 
when broken or cut 
across (Fig. 18). The 
fibers vary in size from 
iroio o to ¥I {oo o f an 
inch, the larger fibers 
being found in the lig- 
amentum subflava and 
the finer ones in the 
vocal cords. They yield, 



Fig. 18. —Yellow Elastic Tissue. 
From teased specimen. (Brinckley.) 

on boiling, a substance called elastin, while the white fibers 
yield gelatin. 

Distribution. — It is found in the ligament between the 
arches of the vertebrae, the walls of the trachea and its 
branches, with other textures in the coats of the arteries, 
and as the principal part of ligaments, in the areolar tissue, 
in the true skin, and mucous membrane. 

4. Retiform or Adenoid Tissue. — Structure. — It con- 
sists of a very fine network of fibers continuous with the 
white fibers of ordinary connective tissue, having few or no 
elastic fibers. Around the fibers of the network are the cells 
which give the tissue the appearance of being a form of stel- 
lated cells with their anastomosing branches when the cells 
are not cleared away. The meshes of the network are occu- 
pied with lymph and by numerous corpuscles (lymphoid 
cells) resembling lymph corpuscles. 




CONNECTIVE TISSUE. 27 

Distribution. — This is a variety of areolar tissue. It is 
found in the spleen, lymphatic glands, the tonsils, and in 
many mucous membranes. 

5. Adipose Tissue, or Fat. — Origin and Structure. — 

This is developed from areolar tissue, the protoplasm of the 

cells having for the most part been replaced by oil, the cell 

wall serving as a capsule, and the fibrous element almost 

disappearing. Under the microscope fat is found to consist 

of cells or vesicles collected into lobules, these lobules being 

collected into clusters, which to the naked eye have the 

appearance of granules; the cells and lobules are supported 

by a small amount of areolar tissue 

in which the blood vessels ramify. 

Each lobule has an afferent artery, 

capillaries, and an efferent vein, 

but no nerves. The cells are round 

or oval, and vary in size from -g^ ¥ 

to s\i) of an inch. 

Nature of Fat. — Fats consist of 
stearin, olein, and palmitin. Dur- 
iug life the fat is fluid, but becomes ^du^ZZ ZZot 
solid after death. Fat ofteu forms & c S5wSS J S S^S*^ ^t£S 
into needle-shaped crystals. S^lffl^W 

Use. — This tissue serves as a protective packing material, 
preventing the heat of the body from passing away too 
rapidly, as it is a poor conductor of heat; it also holds in 
store materials rich in carbon and hydrogen for use in the 
body. During starvation the fat may be absorbed and used 
up in the body, serving as a food, and the cells become ordi- 
nary connective tissue cells. 

Distribution. — While this tissue is distributed quite gen- 
erally throughout the body, it is more abundant beneath the 
skin, around the kidneys, upon the furrow, on the surface of 
the heart, and it is abundant in the marrow, but is absent 
from the lungs and brain. 

6. Mucous or Jelly-like Connective Tissue. — This is 
found in the vitreous humor of the eye, and in the body 
during early development. 




28 



THE MICROSCOPIC STRUCTURE OF THE BODY. 



B. Cartilage. — Nature and Structure. — This is a tough, 
dense tissue, very elastic, yielding to pressure or torsion, hut 
returning to its shape when pressure is removed. 

In color it is bluish white, opaque in mass, but trans- 
lucent in thin slices. On prolonged boiling it yields an 
albuminoid substance called chondrin, which, on cooling, 
hardens like jelly. 

No nerves have been found in cartilage. As it has no 
blood vessels, it derives its nourishment by imbibition of 




Fig. 20.— Hyaline Cartilage. 
1. Perichondrium. 2. Matrix. 3. Cartilage cells. (Brinckley, 0. W. B.) 

lymph which exudes from the neighboring capillaries ; i. e., 
from those of the perichondrium, or from the vessels of the 
synovial interarticular cartilage. Cartilage has an investing 
vascular membrane composed chiefly of white fibers, called 
the perichondrium. This membrane is found in all cartilage ; 
under the microscope cartilage is seen to be made up of a 
ground substance, or matrix, in which are imbedded nucle- 
ated cells. The matrix is without distinct structure (homo- 
geneous), or fibrous. This gives rise to two principal varie- 
ties, viz. : — 



CARTILAGE. 29 

1. Hyaline Cartilage. — This cartilage receives its name 
from a Greek word meaning glass, from its clear appearance ; 
has an almost structureless matrix resembling ground glass, 
in which the cells are imbedded in the patches of irregularly 
shaped cells. In the adult it occurs in the costal cartilage, 
the nasal cartilage, investing the ends of bones (Fig. 20), 
in articulations, in the larynx, the trachea, and the bronchi. 
In young animals it is found in a temporary form, which in 
time is replaced by bone through the deposit of lime salt. 

2. Fibro-cartilage. — In this the matrix has~ a well- 
marked fibrous structure. 
The varieties are : — 

a. Yellow Elastic Carti- 
lage. — In this the matrix 
consists of fine interlacing 
elastic fibers, in which are 




imbedded numerous oval- 
shaped cells, each having a 
well-marked nucleus and 
nucleolus. It is more flex- 
ible and tough than hyaline 
cartilage. It is found in the FlQ 21 ._ 0el ^^^ ic carting* 
cornicula of the larynx, from ear of mouse. (Brinckiey.s.D.o.) 
the epiglottis, the Eustachian tube, and the external ear. 

b. ^Yhite Fibro-cartilage. — This in structure closely re- 
sembles the yellow variety, but has fibers which closely 
resemble those of the white fibrous tissue. 

It is found in (1) interarticular cartilage, as the knee- 
joint; (2) in the marginal cartilage around the rim of the 
shoulder and hip joint; (3) in connecting cartilage, as in the 
intervertebral fibro-cartilage ; (4) in sheaths of tendons. 

Uses of Cartilage. — Cartilage has a number of important 
uses. It binds bones together, and yet allows a certain degree 
of movement, as in the vertebrae; it affords attachment for 
muscles and ligaments; it deepens joint cavities, as in the 
acetabulum; it gives firmness, protection, and support, as in 
the pinna, the larynx, the chest; it maintains the shape of 



THE MICROSCOPIC STRUCTURE OP THE BODY. 

./rib. 




Fig. 22. —Transverse Section of Compact Bone (of Humerus). 
Three of the Haversian canals are seen, with their concentric rings; also the 
lacunae, with the canaliculi extending from them across the direction of the 
lamellae. The Haversian apertures were filled with debris in grinding down 
the section, and therefore appear black in the figure which represents the object 
as viewed with transmitted light. The Haversian systems are so closely 
packed in this section that scarcely any interstitial lamellae are visible, x 150. 
(Sharpey.) 

tubes, as in the trachea 
and the bronchi ; it acts 
as a cushion to deaden 
shocks, as between in- 
terarticular cartilage : 
and lessens friction, as 
in articular cartilage 
of the long bones. 

C. Bone and Dentine. 
— While these two sub- 
stances resemble one an- 
other in composition 
and firmness, they 
differ very much in 
their structure, origin, 
and function. We shall 
defer this study until 

Longitudinal section from the human ulna, we COme to them ill 
showing Haversian canals, lacunae, and can- ■, . . ^ 

alicuii. (Roiiett.) their respective places. 




NUTRITIVE TISSUE. 31 

V. The Nutritive Tissue. — The nutritive tissue is com- 
posed of the blood and the lymph. The blood is the liquid 
which circulates through the veins, arteries, and capillaries. 
It is composed of a liquid (plasma) in which float micro- 
scopic bodies (corpuscles). Its chief function is to carry 
food material to, and waste products from, the tissue. 

The lymph is very much like the blood in composition, 
but has no red corpuscles. 

The lymph bathes the tissues, anil removes waste prod- 
ucts which find their way to the blood vessels by means of 
the lymph veins. 



CHAPTER III. 

ANATOMICAL ELEMENTS. 
EXPERIMENTS. 

1. Carefully tease out some of the fleshy part (pulp) 
of an apple, mount in«iormal saline solution, and examine 
with a low power (one-half or three-fourths objective). Of 
what is the flesh of the apple composed ? Make a drawing 
of the cells, and carefully note their structure. Treat with 
a weak solution of iodine, and again examine. What differ- 
ence do you note ? 

2. Make a very thin transverse section of the pith of an 
elder-stem. Place on a glass slide, with a drop of water or 
glycerin, and examine, first with a low power, and then 
with a high power. Of what is the pith composed ? Have 
you seen anything similar to what you observe in the pith ? 

3. Make a thin section of the dandelion (Taraxacum) 
stem, and put into a forty-per-cent solution of alcohol; then 
into sixty- and eighty-per-cent, keeping the section in each 
solution thirty or forty minutes. Put twenty or thirty drops 
of picrocarmine solution into a watch crystal. Place in this 
solution the sections, and let them remain until they are well 
colored, which will require from fifteen to twenty minutes, 
after which transfer them to ninety-per-cent alcohol, and let 
them remain there from ten to thirty minutes. Next place 
the sections in spirits of turpentine for five or ten minutes; 
watch them carefully, and if they shrink or curl up at the 
edges, remove them at once. Take a clean glass slide, and 
place near its center a drop of dammar or Canada balsam. 
Place on this one of the sections. Take a clean cover glass 
by the points of the forceps, and place it over the section 
so that the opposite edge of the cover glass will touch first, 
and lower it gradually, to avoid the formation of air bubbles 
underneath. Gently press down the cover glass. Examine 
with a one-sixth objective. Observe (1) the bounding mem- 
brane (cell wall), (2) the granular substance within the 
wall (protoplasm or cell body or cytoplasm), (3) a more 

32 



EXPERIMENTS. 33 

highly colored part (nucleus), (4) a point within the nucleus 
(nucleolus). 

4. With a horn spatula or ivory paper knife scrape the 
hack of the tongue or the inside of the cheeks or lips. Place 
the suhstance thus obtained on a clean slide, and cover with 
a cover glass, adding a drop of water if needed. Examine 
it with the microscope, using one-fourth or one-sixth objec- 
tive, and make a drawing. 

5. Examine in a normal salt solution with a high power 
the hairs which grow upon the stamens of the Spiderwort 
(Tradescantia). Try to determine the parts. Note the pro- 
toplasm, forming a layer lining the wall, heaped up around 
the nucleus, and sending off fibrous-like processes to vari- 
ous parts of the cell. Notice the currents of granular sub- 
stance in the fibers, sometimes from the nucleus, sometimes 
toward it. What property of protoplasm do you learn from 
this experiment ? Warm the slides as directed in the Appen- 
dix. Increase the temperature, and notice the effect. 

6. Place a drop of water containing amoeba} on a slide ; 
cover with a cover glass, being careful to avoid pressure, 
and search over it with a one-fourth-inch objective; if you 
find an amoeba, examine it with a one-eighth-inch objective. 
Observe its outline, structure, and movements. Make draw- 
ings of it at intervals of five seconds or more. Describe what 
you see. What do you learn of the properties of the cell 
from this ? Heat the slide as directed above, and note the 
effect. 

Amoeba? may be found in mud, stagnant water, or in 
vegetable infusions. 

7. Prick your finger, press out a drop of blood, and 
spread it out on a slide under a cover glass, avoiding pres- 
sure ; then surround the margin of the glass with vaseline 
or oil. The white corpuscles may be recognized by their 
larger size, and by being less numerous. Observe their size, 
structure, form, and movements. 

Make drawings of the more remarkable forms which they 
assume. In order to keep the colorless corpuscles so that 
they will retain their vitality and movement, it is necessary 
to keep the glass slide warm. This may be done by the 
method given in the Appendix. The blood of man should 
be kept at a temperature of 38° C. 

8. Get a number of frogs' eggs or snails' eggs, and put 

3 



34 ANATOMICAL ELEMENTS. 

them in water in a warm place, and carefully note by means 
of the microscope the changes which take place. What do 
you learn by this of the properties of the cell ? of its relation 
to tissues ? of the origin and development of the animal % 

9. Get from a pond or a brook some stagnant water. It 
will usually contain a great number of little plants and 
animals. Keep them in water in a warm place, and in the 
sunlight, and observe them from day to day. Write a de- 
scription of the things you have seen. What do you learn 
from this experiment ? 

10. Secure some fish eggs; tease out the mass, and stain 




Fig. 24. — Gelatinous Tissue of Infra-orbital Fossa of Rabbit. 

a. Bundles of connective tissue, b. Flat branched cell. c. Branched cell 
seen from the side. d. Cell of doubtful origin. (Sanderson.) 

a number of eggs by placing them in picrocarmine, and then 
examine them with a high power. Make a drawing of the 
nucleus in the different specimens examined. 

11. Secure some of the pollen of the wild onion; color it 
with picrocarmine, and examine it with a high power. Make 
drawings of what you see. In this experiment and in Experi- 
ment 10 you may be able to observe the nuclear division 
described on page 41 (Fig. 30). 

12. Get a piece of a large ligament (ligamentum nuchce), 
(a) tease it out as fine as possible in water, and examine a 




Fig. 36 




1. Stylo-hyoid. 2. Digastric (posterior body). 
gland 5. Digastric (anterior body). 6. Sterno-hyoid. 7. Omo-hyoid. 



PLATE IT. 
Fig. 35.— Muscles of the Neck. 

Duct of Maxillary eland, 4. Submaxillary 
I. 7. Omo-hyoid. 8. Sterno-cleido-mastoid. 
9. Scaleni. 1U. Splenius. 11. Trapezius. 

Fig. 36.— Muscles of the Face. 

1. Tarsal ligament. 2. Nasal. 3. Quadratus labii superioris. 4. Orbicularis oris- 5. Quad- 
ratus labii inferioris- 6. Depressor anguli oris (Triangularis). 7. Platysma. 8. Risorius. 9. 
Zygomaticus major. 10. Orbicularis palpebrarum. 11. Occipito frontalis. 

Fig. 37 ^..—Muscles of Mastication. 

1. Temporal. 2 Masseter. 

Fig. 37 B.— Muscles of Mastication. 

1. External pterygoid. 2 Internal pterygoid. 
Fig. 3S. Muscles of Mastication. 
1. Zygomaticus major 2. Zygomaticus minor. 8. Levator labii superioris. 4- Levator 
angulioris. 5. Triangularis. 7. .Masseter. 8 Buccinator. 9. Duct of parotid gland. 



EXPERIMENTS. 35 

small portion in water or glycerin. How are the fibers ar- 
ranged ? Do they branch? (b) Treat a teased piece with 
acetic acid. What change do yon notice ? 

13. Mince np several pieces of the ligament yon get for 
Experiment 12, and boil in water for some time. Set away 
to cool. What change has taken place ? 

14. Cut from a recently killed frog or rabbit a piece 
of the tendon that extends the toes, (a) Place for ten or 
fifteen minutes in a five- to ten-per-cent solution of common 
salt. This will enable the tendon to be more easily teased. 
Tease as fine as possible. Mount in water or glycerin, exam- 
ine with a high power, and observe carefully the arrangement 
of the fibers. Compare this observation with Experiment 
12. (b) Treat a teased portion with acetic acid. "What 
change do you note ? Compare the action of acetic acid 
in this case with that of (b) in Experiment 12. 

15. Clip a number of pieces of tendons; boil them in 
water for several hours, and set them away to cool. How 
does the result you get compare with that of Experiment 12 ? 

Name three ways in which yellow elastic tissue differs 
from inelastic tissue, as shown by the experiments yon have 
tried. Which of these is best adapted for attachments of 
muscles ? which for ligaments ? which in ligaments where 
great freedom of motion is required ? How could yon show 
that both elastic and inelastic fibers are present in a tissue ? 
By your test (b) of Experiments 14 and 15, test the tissue 
that binds muscles, the lower layer of the skin, the coats of 
the aorta, the tendons of the muscles, a thin slice of cartilage. 

ANATOMICAL ELEMENTS. TEXT. 

A muscle, a nerve, or the skin seems to be a simple struc- 
ture, but an examination with the microscope shows it to be 
very complex. 

As we have already learned, these organs are made up 
of simpler parts called tissues. The tissues, on examina- 
tion, are found to be composed of still simpler parts. Most 
tissues may be reduced to two or three simple elements : one, 
a structureless, thread-like body — the fibers ; the other, a 
more or less spherical body — the cell, bound together by a 
cementing substance, or matrix. Since these two structures 



36 



ANATOMICAL ELEMENTS. 



enter into the make-up of the various tissues of the body, 
they are called anatomical elements. While these structures 
are microscopic in size, they are very important, and deserve 
our careful study. 

The Cell. — From our observation we have already 
learned that cells differ greatly in size, form, and structure. 
Corresponding with this difference of structure and compo- 
sition will be found a difference of function and properties. 
We shall find it true throughout the whole organic world that 
a difference of form implies a difference in physiological 

action. As saws, 
knives, and chis- 
els vary in form 
to adapt them to 
different uses, so 
cells differ that 
they may do dif- 
ferent work. 

The typical 
form of the cell 
is spherical, as 
seen in the egg 
of the frog or the 
snail. In process 
of the develop- 
in e n t of the 
plant and the animal, they become greatly modified from 
inherent forces or external cause, as pressure or similar influ- 
ences. We have observed the globular and the flattened cell 
(Fig. 26) in drops of saliva; columnar, in various parts of 
the mucous membrane (Fig. 10) ; columnar with the free 
portion provided with hair-like processes (cilia) (Fig. 9), 
as in the mucous membrane of the nasal fossae, upper part 
of the pharynx, the trachea, the lungs, and other parts of the 
body; fusiform, in the cells of the involuntary muscles (Fig. 
15) ; stellate, in some nerve cells (Fig. 83); pear-shaped, 
as in the cells of the ganglion of the spinal nerve; flask- 




Fig. 25. Glandular Tissue. 
Section of part of submaxillary gland 
1. A duct. 2. Orescent cells. 3. Blood vessel, 
cells. 5. Mucous cells. 



(human). 
4. Serous 



THE CELL. 



37 




shaped, in the goblet cells (Fig. 26) of the mucous mem- 
brane; fibrillated, in the skeletal muscle (Fig. 14); and 
caudate, with numerous branches (poles), some of which 
branch into numerous tree-like branches (arborescent) (Fig. 
85). Cells vary in size from ^o to ^in diameter, and 
5 oV o t° one-half inch or more in length. 
While cells under low power seem 
to be very simple, under high power 
they appear very complex. Typi- 
cally, the cell (Fig. 32) consists of 
an investing membrane (cell wall) ; FlQ o 6> _ G0BLET Cells 
of a firmer part, making up the £?°^ to ^J™ us Membbane 
greater part of the cell , the body sub- 
stance (cytoplasm), in which we recognize a more or less 
opaque network (spongio plasm), inclosing and ramifying a 
clear fluid substance (Fig. 32) (hyaloplasm). Near the 
center of the protoplasm is a spherical firmer portion, — 
the nucleus. By special preparation we find the nucleus 
is composed of a clear fluid called nucleoplasm, and a net- 
work of fibers called chromo plasm. In the nucleus of 
many cells is to be found one or more small points called 
nucleoli. 1 



i Physical Structure of Protoplasm.— Although this subject has received 
extended and careful study, and with the aid of improved histological 
methods, yet we are still much in doubt as to the structure of protoplasm. 
While histologists are generally agreed as to the appearance and the parts 
of protoplasm, as seen under high power, they are not agreed as to the inter- 
pretations of the appearance. Under very high power, and by proper staining, 
protoplasm appears as a meshwork, composed of fine granules suspended in a 
clearer substance, the spaces of the meshes being composed of a third clearer 
substance. 

The three more important interpretations of this appearance are, (1) "that 
protoplasm is composed of a clear, viscous substance, in which are imbedded 
many fine granules of denser substances and numerous larger globules of a 
clearer, more liquid substance; " (2) " that the fine spots, which appear to be 
granules, are simply cross-sections of fine threads of denser protoplasm which 
lie coiled and tangled in the clearer protoplasm; " (3) " that protoplasm exists as 
a framework, being a viscous liquid containing many fine globules of a liquid 
of diif erent density and numerous larger globules of a fluid of still other density." 
The foam does not consist of bubbles filled with air, but of protoplasm of different 
density. The last theory is the one more generally accepted by the majority of 
modern naturalists. 

We are even more in doubt as to the chemical constitution of protoplasm than 
we are as to its physical structure. We thus know little of the real nature of 
protoplasm, which is considered to be the fundamental life substance. 



38 



ANATOMICAL ELEMENTS. 



Histologists are not agreed as to the nature of the 
nucleoli. Some consider them as knots formed by the cross- 
ing of the meshes of the chromoplasm, while by others they 
are considered as a distinct structure. Most animal cells are 
without cell walls. 

There are some cells so simple that they seem to be devoid 
of cell wall and nucleus, and consist only of protoplasm, as 
seen in some of the so-called animals, as the protomyxa. 

While the cells in the different tissues vary in their com- 
position, they consist primarily of from eighty to eighty-five 





Fig. 27.— Forms Assumed by an Amceba in Thirty Minutes' Observation. 

As the coverings protrude, the protoplasm seems to flow with the projecting 
part and hackward again as tbe projecting part retracts. (Brinckley.) 

1. Nucleus. 2. Granules. 3. Vacuole. 4. Cell wall. 

per cent water. The solids consist chiefly of proteids, the 
principal one of which is plastin ; of carbohydrates, the prin- 
cipal of which is glycogen, a kind of starch ; and of mineral 
salts. 

We can best learn the properties of the cell by the care- 
ful examination of a little microscopic animal, the amoeba 
(Fig. 27), or the white corpuscles. 

The amceba consists of a single cell, and to live it must 
move, breathe, digest, secrete, excrete, etc. ; and yet we find 
no special parts for these functions, but all parts of the cell 
seem to have their respective functions. 

From a careful study of this little animal we learn, (1) 
that cells have the power to be awakened to action, i. e., have 
irritability; (2) that they may change their form — con- 
tract; (3) that they can appropriate material, and make it 
like their own substance — assimilate; 1 (4) that they can 



i Protoplasm also has the power of taking up some substances and reject- 
ing others. This power to select one substance and reject others is called 
selective absorption. This explains, in part, why a drug will affect one tissue and 



THE CELL. 39 

do chemical work by making compounds; (5) that they have 
the power of forming by their division, either directly or 
indirectly, new cells. 

When the animal is composed of many cells, the work 
of living becomes divided, some cells taking upon them- 
selves the whole work of contraction, some that of feeling, 
some respiration, some digestion, and some excretion and 
secretion. 

In the human body we have the muscle cells for con- 
traction, the nerve cells for feeling, those of the lungs for 
respiration, those of the alimentary canal for digestion, and 
those of the kidneys for excretion. 

The cells' taking upon themselves some part of the work 
of living is called division of labor. To better enable the 
cells to perform their respective work, we find them differing 
in form and structure. The changing of the cells from a 
simpler to a more complex form and composition is called 
differentiation, and it is a well-established biological prin- 
ciple that the differentiation of form (morphological differ- 
entiation) is accompanied by differentiation of function 
(physiological differentiation). 

Metabolism. — All the activities of the body must be 
brought about by the activity of the cell. It is the only 
vital part of the body, the other parts being mere skeletal 
structures. 1 



not others ; why one drug will be a cerebral stimulus and another a vasomotor. 
Thus it is that the blood stream, laden with mineral salts, passes the muscles 
unaffected, but in passing through the bone tissues loses part of its calcium 
phosphate and calcium carbonate. 

iln its development the frog's egg passes through the following stages: — 

1. The protoplasm within the cell wall divides into numerous cells, and at 
each subdivision the cells become smaller, passing through what is called the 
segmentation stage. (Fig. 31.) 

2. As a Tesult of this continued segmentation, there is formed a body which 
has the appearance of a mulberry, and hence is called the morula stage (Fig. 31), 
in which the cells become crowded to the outer part of the inclosing capsule. 

3. Following this later stage, the cells in the upper part become somewhat 
different from those of the lower part, and the sphere becomes pitted (resembling 
Fig. 31), when it is known as the gastrula stage. 

4. The cells continue to multiply, and form a body (like e, Fig. 31), in which there 
aro three well-marked cell layers, differing in the form and size of the cells com- 
posing them. The body is now known as the hlastoderm, and consists of the upper 



40 ANATOMICAL ELEMENTS. 

It is in the little laboratory of the cell that are manufac- 
tured the various materials of the body. It is the cell that 
does the work of secretion and of excretion; that is the 




Fig. 28. — Internal, Cell. Division. 

Hyaline cartilage from the toe of a chicken. 1. Old cell wall. 2. New cells. 
3. Nucleus. (Brinckley, O. W. B.) 

source of the energy of the body, whether it be motion, heat, 
or nerve stimulus. 

The varied activity by which the cells perform this func- 
tion is called metabolism. 



layer of cells, called the epiblast; a middle layer of cells, the mesoblast; and the 
lower layer of cells, the hypoblast. 

From the epiblast are formed the skin (epidermis), the nervous system, and 
organs of special sense (in part); from the mesoblast is formed the skeleton, 
muscles of circulation, connective tissue, the true skin (derma), the spleen, the 
kidneys, and the bladder (except the lining, which is derived from the hypoblast) ; 
from the hypoblast are formed the mucous membrane, the alimentary tract, the 
liver, the pancreas, and the lungs. 



THE CELL. 



41 



When the process is constructive in its effect, i. e., 
tends to build up living material, or when complex sulh 
stances are made from those that are simpler, it is called 
anabolism. The breaking down of complex substances into 
simpler ones, by which potential energy is converted into 
kinetic energy of motion or heat or life force, is called 
katabolism. 
* The process by which the meat, the bread, the butter, 
and the fruit we eat is converted into muscle, nerve, bone, 
and brain tissue is anabolism. That by which the tissue 
uses up material to produce motion and heat, and by 
which the waste products, carbon diox- 
ide, urea, and water, are produced, is ka- 
tabolism. 

Cell Multiplication.— As we have al- 
ready seen, cells have the power of produc- 
ing new cells. When the cells produced are 
destined to become new individuals, the 
process is called reproduction; when they 
are to form new tissue, and augment the 
size of the body, the process is called 
growth. 

The principle that all cells proceed from 
pre-existing cells, is the basis of biological miSSS^a'shS 1 ^ 
science. The body of all animals or plants jf>3|^^ 
consists either of one cell or of many cells mentst (After Fiem- 
and their products. ming ' 

Cells multiply in various ways, the most common of 
which are direct cell division, internal cell division, and 
indirect cell division. 

Cell Division. — The division of the cell is preceded by 
division of its nucleus. 1 Nuclear division may be either 
(1) simple, or direct (amitotic), which consists in the simple 

i The Centrosome.— This is a little body which is continually present with the 
nucleus. The centrosome possesses a peculiar attraction for the protoplasmic 
filaments and granules in its vicinity, producing a stellate appearance, like Fig. 
29. The centrosome, with the attracted filaments, is called the attraction sphere, 
and plays a very important part in the division of the nucleus, but it is not 
probably the first cause of the process of division. 




Fig. 29. 



42 



ANATOMICAL ELEMENTS. 



exact division of the nucleus into two equal parts "by con- 
striction in the center, and may have been preceded by the 
division of the nucleoli; or (2) indirect (miotic), which con- 

sists in a 
series of 
changes, the 
complexity of 
which varies 
i n different 
cells. 1 

FIBERS. 

Kinds of 
Fibers. — Fi- 
bers are of 

B two kinds, y el- 
he 

wreath or rosette form. E. The aster, or single star. F. A 

nuclear spindle from the Descemet's endothelium of the V^ll™*r flU VQ 

frog's cornea. G, H, I. Diaster stage. K. Two daughter -l^iiuw uucis 

nuclei. (Klein.) haye & yeUow 

tinge, are very elastic and often give off branches, and anas- 
tomose with other fibers. They give firmness and elasticity 
to the parts in which they are found. They make up the 
greater part of many tendons ; are found in the middle coats 
of the arteries, the pulmonary alveoli, and in various parts 
of the body in connection with white fibers. They vary in 
size from 




F 
Fig. 30. 



G H 

Indirect Cell Division (Karyokinesis) 



A. Ordinary nucleus of a columnar epithelial cell. 
C. The same nucleus in the_stage of convolution. D. The Inyj and wllitc 



-fr-Q-Q to g 4V o" °^ an inch in diameter. 



On boiling 



iln most cells these changes are as follows, as observed by Klein: 1. The 
nucleus in the resting conditions consists of a very close meshwork of fibrils 
(chromoplasm) imbedded in protoplasm (nucleoplasm), and surrounded with an 
envelope. 2. The enlargement and disappearance of the envelope, and the 
increase in thickness of the nuclear fibrils, which, being more separated, stain 
better (stage of convolution) (Fig. 30). 3. The arrangement of the fibrils into 
some definite figure by an alternate looping] in and out around a central space, 
forming a rosette or wreath (rosette or wreath stage). 4. The loops of the rosette 
now become divided at their circumference, and their central points become 
more angular, so that the fibrils divide into portions of about equal length, as if 
doubled at an acute angle, and radiate V-shaped from the center, forming a star 
or wheel, or, in some cells, from two centers, forming a double star (diaster) (the 
aster stage). 5. After remaining almost unchanged for some time the V shape 
being rearranged in the center, side by side, point of V outward, tends to sepa- 
rate into two bundles, which gradually assume position at either pole (nuclear 
spindle stage). 6. From these groups of fibrils the two nuclei of the new cells are 
formed (daughter nuclei stage). The stages through which they pass before 
reaching the resting condition are just the same as those passed through by 



FIBERS. 



43 



tliey do not yield gelatin, but a substance called elastine. 
They are unaffected by acetic acid. 

White fibers, when forming a compact tissue, as a tendon, 
have a shining, pearly appearance, are very strong, and 
pliant, and inelastic. When examined with a high power, a 
teased specimen of a small bundle of white fibers is seen 



to consist of very 

of an inch in diameter 



fine transparent fibers of from Tlf J T ¥ 



to 



sTinrir 



These fibers do not occur 




Fig. 31.— Stages of Development. 

a. Ovum. h. Segmentation stage, c. Morula stage, d. Gastrula stage, e. 
Blastoderm. 1. Epiblast. 2. Mesoblast. 3. Hypoblast. 4. Primitive groove 
(Brinckley.) 

singly, but are cemented by a quantity of the mucin ground 
substance; in contrast with the yellow fibers, in which each 
fiber of a bundle seems parallel with its adjoining fibers, 
neither branching nor uniting with them. While transparent 
with transmitted light, when seen in mass they appear white. 
Acetic acid causes them to swell, and become almost invisible. 
On boiling with water they yield gelatin. 

They are found in the wavy bundles of areolar tissue ; 



the original nucleus (mother nucleus), but in reverse order; viz., the star, the 
rosette, and the convolution. During or soon after the formation of the daughter 
nuclei, the cell itself becomes contracted, and then divides in a line about 
midway between them. These changes will be clearly understood by a careful 
study of Fig. 30. It is now believed that the indirect nuclear division (miotic) 
is very nearly universal, if not entirely so. Many cells are being formed every 
moment of our lives to keep up the growth of the body, and to supply those 
that become transformed. The changes which we have described in nuclear 
division are taking place continually. _ 



44 ANATOMICAL ELEMENTS. 

in parallel bundles to form compact bundles or cords, as in 
tendons and ligaments: they form fibrous membrane, as the 
periosteum, covering the bones ; the perichondrium, covering 
the cartilage; the dura mater, lining the skull; and the 
fascice, enveloping and binding together the muscles. In 
the true skin and mucous membrane the bundles of inter- 
lacing white fibers form a close felt-work. 

White and yellow fibers generally occur together in 
tissues, and the relative proportion of each will in a large 
degree determine the property of the tissue ; the white fibers 
giving firmness and inelasticity, and the yellow elasticity. 

As to how these fibers originate, histologists are not 
agreed. Some think they are formed by the modification 
of the substance which the cells throw out between them- 
selves, known as intercellular substance; others that they 
are modified forms of branched cells, the branches of which 
have become joined and then reduced. 



CHAPTER IV. 

THE MUSCULAR SYSTEM. 
EXPERIMENTS AND DEMONSTRATIONS. 

1. Place the arm on the table so that it rests on the 
forearm. Grasp the upper part of the arm with the left 
hand, and gradually bend the arm. What change do you 
note in the muscle ? Let the arm return gradually to its 
first position. What change do you note I The first condi- 
tion is called a contraction, the second a relaxation. 

2. Straighten the 
arm, grasp it so that 
the fingers will press 
upon the upper part 
of the arm, and the 
thumb upon the 
lower. Gradually 
bend the forearm* 
and notice what 
change takes place in 

the upper muscle of ^^^^^^-^^ ^-i 

the arm and also in FlG- ^.-typical Cell, (ideal.) 

the lower. Extend 1. Cell wall. 2. Reticulum (Spongioplasm). 3. 

, TT r i Paraplasma (Hyaloplasm). 4. Membrane of nu- 

t 11 6 arm. \\ n a t cleus. 5. Nucleoplasm. 6. Chromoplasm. 7. Nu- 

i i , cleolus. 8. Cytoplasm. 

change do you note 

in the biceps ? How does it compare with the first condi- 
tion ? Try other muscles. What does this teach you in 
regard to the arrangement of muscle ? 

3. Obtain a rat or a cat, and prepare it for dissection. 
(See Appendix.) Remove the skin, and carefully notice 
appearance and arrangement of the flesh (7nuscles). Care- 
fully dissect off the covering (fascia). To what are the 
muscles attached ? How are they connected \ Of what two 
parts are some of the muscles composed? (See Pig. 48.) 
Examine the nature of the tendons. What advantage does 
it give the muscle for the tendons to be inelastic ? 

4. Remove the muscle (the muscle should be fresh) of 
the calf of the leg. Attach one tendon to a firm sup- 
port, and to the other tendon fasten a weight, gradually 

45 




46 THE MUSCULAR SYSTEM. 

increasing the weight. Is there any change in length ? Re- 
move the weight. Does the muscle return to its former 
length ? What property does this show the muscle to pos- 
sess ? Try the same experiment with a muscle that has been 
killed by immersing it in water at 40° C. (140° E.). 

5. Examine the muscles for the different modes of 
arrangement of the tendons. Make drawings of what you 
observe, and compare them with those given in Fig. 34. 

6. Examine carefully the tendons of the muscles dis- 
sected. Pull on the tendons to determine their action. Dis- 
sect out the muscles of the leg of a cat or a chicken. Notice 
how the tendons work. 

7. Dissect out one of the muscles of the leg of a frog. 
Tie it by its tendons to a stick, so that it will remain extended. 
Preserve by keeping in alcohol (80 per cent). Tear off a 
small piece, and tease it out as fine as possible in dilute 
glycerin. Examine under high and low power. Note, (a) 
the varying size of the threads (fibers) ; (b) the marking of 
the fibers (striation), which under high power are seen to be 
made up of alternate dim and bright crossbands. (c) Do the 
fibers break up into finer threads (fibrillce) ? (d) Treat 
a specimen in a similar manner that has been preserved in 
picric acid. Do the fibers break up in more than one direc- 
tion? Examine the surface of the disks. Make drawings 
of your observations, and compare them with those in this 
book. 

8. Remove the covering of a frog's muscle, and tear off a 
small portion of the flesh. Tease so as to show the fibers. 
Press on some of the fibers with a bristle; this will break 
the muscle substance, and leave uninjured the delicate cover- 
ing (sarcolemma) of the fiber. 

9. To fibers teased the long way of the muscle, add a 
five-per-cent solution of acetic acid. Note the changes that 
take place. When the fibers have become transparent, 
notice the numerous dots (nuclei) scattered throughout the 
muscle substance. Make a careful drawing of their appear- 
ance. 

10. Imbed in paraffin a small piece (a cross-section of a 
muscle) which has been hardened in a five-per-cent solution 
of chromic acid ; make a thin transverse section, stain in hem- 
atoxylin, and mount in glycerin. Observe, (a) the connect- 



EXPERIMENTS. 47 

ive tissue (cpimyshim) which surrounds the bundles of 
fibers and the whole muscle, which gives off connective tissue 
(cndomysium) between the muscle fibers; (b) the relation 
of the nuclei. 

11. From the peritoneum of the intestine of a recently 
killed animal tear off with fine forceps a piece as thin as 
possible of the longitudinal muscular coat. Put in a one- 
per-cent solution of potassium dichromate or in a thirty-per- 
cent solution of alcohol for two days, wash with water, stain 
in picrocarmine, wash to remove excess of coloring, tease 
out in dilute glycerin. Note, (a) the form and arrangement 
of the muscle cells; (b) the arrangement of the fibers. 

12. Treat a piece as in Experiment 9, teasing it out in 
a normal salt solution. Examine it, and then acid a one- to 
five-per-cent solution of acetic acid, and note the change in 
the appearance of the cells. 

13. Take a small piece of the heart of a frog or a rat, 
and preserve it in potassium dichromate solution. Take a 
small piece, tease it out thoroughly, and mount in glycerin. 
Carefully observe, (a) the form, size, and arrangement of 
the cells; (b) that the fibers have no sarcolemma. (c) Stain 
some of the teased fibers in picrocarmine to make the nuclei 
more prominent, (d) Note the branching of some of the 
cells. 

14. Destroy the brain and spinal cord of a frog, and 
expose the sciatic nerve, at about the upper third of the 
thigh, where the artery (femoral) gives off two transverse 
fibers, from point down to the knee; isolate the nerve by i 
cutting away the connective tissue. Care should be taken 
not to injure the nerve by pinching it, or by putting too 
great a strain upon it, and also not to injure the artery. 

Take a pair of electrodes which have platinum points on 
one side, and connect with two Grenet cells connected in 
series; interpose a key so as to short-circuit the current (Fig. 
33). Close the circuit. Place the electrode under the nerve 
so that the electrode alone touches it. Notice that, in only 
very rare cases, there is movement of the muscles when the 
circuit is opened and closed. Do not repeat the experiment 
more than once or twice, as it tends to exhaust the nerve, and 
render it unfit for the other experiments for which you will 
need this preparation. 

What is the effect of a constant galvanic current ? 



EXPERIMENTS. 



49 



15. Introduce into the circuit of Experiment 14 an 
induction machine, having primary and secondary coils (see 
Fig. 33). Open and close the key several times. Notice, 
(a) that each closing and opening, which produces a single 
induction, causes a single contraction of the muscle. Do not 
use too strong a current ; begin with the weaker current, and 
generally increase by the means of the secondary coil, push- 
ing it farther in the primary to increase the current, until 
you get a well-marked contraction, (b) Open and close the 
keys as rapidly as you can for a few seconds, which produces 
a continual contraction (tetanus) of the muscle. Open the 
circuit, and notice the flaccid condition of the muscle. 




a. Penniform. 



Fig. 34.— Forms of Muscles. 
Bipemriform. c. Radiate, d. Fusiform, e. Digastric. 



/. Sphincter. 1. Tendon. ~ 2. Body 

16. Expose the sciatic nerve well up the thigh, and cut 
it off as high as you can. Dip the free end of the nerve into 
a saturated solution of common salt (sodium chloride). 
Notice the effect. How has the solution acted ? 

17. Take the preparation of Experiment 16, and cut off 
the portion of the nerve that was in that solution. Pinch 
the end of the nerve several times with the forceps. Notice 
the contraction. 

Anything which calls into action or increases the activity 
of an organ is called a stimulus. From the above experi- 
ments, how many ways have you found of stimulating mus- 
cles ? Can you think of any other way by which they can 
be stimulated ? By what stimulus are most of the move- 
ments of the body produced ? 

18. Dissect out the calf muscle (gastrocnemius) (Figs. 
46 and 47), so as to leave it attached to the head of the 

4 



50 THE MUSCULAR SYSTEM. 

thigh bone (femur), and leave the sciatic nerve intact. 
Remove the bone from its socket (acetabulum) in the hip 
bone (innominatum) , and cut off the bone about an inch 
from the upper end. Now cut off the sciatic nerve as high 
up as possible, being careful not to strain or stretch it. Pre- 
pare the apparatus as shown in Fig. 33. Load the lever 
with ten or twenty grains, and bring it in contact with the 
cylinder of the kymograph, which has been covered with a 
piece of smoked paper. 

Arrange the induction machine so as to produce a single 
induction shock. Set the cylinder of the kymograph to 
rotating rapidly; note'" carefully the effect produced by the 
lever tracing on the smoked paper when the muscle contracts. 
The tracing is called a muscle curve. Make several trac- 
ings. Carefully remove the smoked paper, and put it into 
a shallow pan containing a solution of shellac and alcohol; 
carefully remove and let it dry. This will make the tracings 
permanent, so they can be examined without injuring them. 
If you do not have a kymograph and moist chamber, fair 
results may be obtained by removing the handles from a 
seven-in-one apparatus, and putting in their place two 
spindles, the upper one ending in a cogwheel, so that it can 
be put in motion by clockwork or a weight. The lever for 
the muscle and the tracing may be fixed to a ringstand. The 
muscle-nerve preparation may be kept moist by occasionally 
spraying it with a normal saline solution. (See Appendix.) 

20. With the same apparatus and preparation as in 
Experiment 19, see what effect rapidly repeated induction 
shocks have upon the contraction and the form of the curve. 

From these experiments, how many changes do you notice 
in a muscular contraction ? Does the muscle begin to contract 
the instant you apply the stimulus ? Compare the phase of 
contraction with that of relaxation. 

21. Remove from the thigh of a frog, as soon as possible 
after killing, the long, flat muscle called the sartorius (Fig. 
45). In dissecting out the muscle, take great care not to 
injure the muscle except at its extremities. Place it at once 
in a normal saline solution in a glass vessel, and set it on an 
unheated stage. Put the part least injured under a two- 
thirds objective, and focus down on some object beneath or 
within the muscle ; notice the ease with which it can be seen. 
"Now gradually heat the stage by the apparatus as explained 



EXPERIMENTS. 51 

in the Appendix. Carefully watch the temperature as deter- 
mined by a thermometer placed in the solution containing 
the muscle. Carefully watch the effect of the heat upon the 
transparency of the muscle. Raise the temperature to 40° 
C, which kills the muscle substance, producing the result 
you have observed. 

22. Divide a fresh muscle. Place one portion in water 
at -±0° C, the other in water at 100° C. Test the reaction 
of both. The portion in 40° C. will be found to be acid, 
that in 100° C. to be alkaline. When muscle substance dies, 
it passes gradually into a state called rigor mortis, and in 
so doing becomes acid in its reaction. This is the case in 
the portion at 40° C. Rigor mortis is prevented by placing 
in water at 100° C. ; the muscle therefore retains its normal 
reaction. 

23. (a) Oppose the fingers and thumb, and note action 
of muscles. (6) Stand erect, and raise the hand as in point- 
ing to an object ; note action of muscles. Are there other 
than the arm muscle called into play ? Take a position with 
a ball bat held in your hands as in striking a ball. What 
do you learn in this experiment about the harmony of action 
of muscles ? 

24. Grasp the handles of an induction machine, gradually 
increase the current by means of the core of the secondary 
coil, and carefully note the effect on the muscles. If there 
is a strong current, try to let go of the handle. Why can you 
not let go ? In what condition are the muscles ? 

25. Place one of the metal handles in a basin of water. 
Place a coin in the water. Grasp that handle of the induc- 
tion coil not in the water with your left hand. Put on a 
strong current, and try to remove the coin from the water 
with your right hand. Explain what takes place when the 
hand touches the water. 

26. Have some one lift a heavy weight, and carefully 
notice the expression and condition of his body while lifting 
the weight. Try to lift a heavy weight yourself? What 
muscles are called into play ? Why do you hold your breath ? 
What effect has the lifting and the holding of the breath 
upon the pressure of the great blood vessels ? How do you 
account for the flushed veins ? 

27. Xote carefully the pulse and respiration of the per- 
son performing this experiment ; then have him perform some 



52 THE MUSCULAR SYSTEM. 

vigorous exercise, as running rapidly for a short time. What 
change do you note in the pulse and respiration? How do 
you account for this difference? Why should there be a 
" shortness of breath " ? 

28. !Note your pulse and respiration before and after 
taking a moderate walk. What difference do you note ? Why 
is the body not fatigued, and the pulse and respiration much 
increased ? 

29. Hold the arm out straight for two minutes, and notice 
the effect. ^ T ow alternately flex and extend your arm for 
the same length of time, making the movements moderate. 
How do you account for the difference in weariness produced 
in the two cases ? 

30. Let the arms hang at the side, and take the measure 
of the arm at its larger part. Mex the arm, and take the 
measure of the larger part. What difference do you notice ? 

31. Determine the attachment of the biceps muscle to 
the forearm by slightly flexing the forearm, and passing the 
linger from the upper surface of the elbow joint over the 
tendon that is tense to the point to which it is attached. To 
what bone is it attached ? Determine the upper attachments 
by passing the finger over the shoulder joint, and notice 
what tendon is tense when the forearm is flexed. The tendon 
attached to the fixed point is called the origin; the tendon 
attached to the point of motion, the insertion. 

32. In a similar manner determine the origin and inser- 
tion of the muscles that flex the hand ; that flex the fingers ; 
that extend the hand ; the fingers ; the forearm. Try similar 
experiments with other muscles. What advantage is secured 
by the muscles that move the hand having long tendons, and 
by the muscles being located in the forearm instead of in the 
hand? 

33. Determine the position, origin, and insertion of the 
muscles of the thigh, leg, and foot. Make a record of your 
observations. Examine the illustrations, and determine the 
names of the muscles with which you have experimented. 

34. Examine the skeleton, and see how the insertions and 
origins you have determined correspond with the prominence 
and markings of the surface of the bones. Compare your 
observations with the facts given in the diagram of the prin- 
cipal muscles. Can you give a reason for the prominences 
and markings on the bones ? 



EXPERIMENTS. 53 

35. Make an apparatus like Fig. 34a. Arrange the 
apparatus as in A. Put a four-ounce weight at the end of 
the short arm, and see what weight will balance it on the 
end of the longer arm. What is the ratio of the length of 
the arms as compared with the weights ? What advantage 
is gained by this kind of lever ? Kead in the text the para- 
graph on mechanism of motion, and determine the class to 
which this lever belongs. 

36. Examine the skeleton in connection with Figs. 43 
to 47, and determine what bones form first-class levers. 

37. Arrange the apparatus as in B, and put an eight- 
ounce weight two spaces from the hinge, and determine how 
many ounces it takes to balance the eight-ounce. What class 
of lever does this represent? What advantage is gained by 
this class of lever ? What n 

bones and muscles of the w g ^ g 

body are of this class of ' A ■ 

38. Arrange the ap- fi~^^ ^ »i@==g 

paratus as in C, and put & ' c — ' 

a two-ounce weight at the a. b. 

end of the lever and a six- *• Po ^ e w |i g ^ crum ' L Po 3 e wd g hf rum ' 
teen-ounce weight upon c. 

,i . • ,, °i j 1. Power. 2. Fulcrum. 3. Weight. 

the string, attached one 

space from the hinge. What class of levers does this appa- 
ratus represent ? What bones and muscles of the body form 
this class of lever ? 

39. What class of levers do the following form : the head 
as it is bent backward by the complexi muscles ? by the foot 
in flexion ? by the leg in flexion ? 

40. Carefully dissect out the calf muscle of a rabbit. 
Cut it loose from its tendons. Weigh the muscle, place it 
in a drying oven, and keep it at a temperature of 110° C. 
for several hours until dry. Remove the muscle from the 
oven, and when cool, weigh, and determine loss of weight 
from drying. The loss of weight represents approximately 
the amount of water in the muscle. What per cent of the 
muscle is water ? 

If you do not have an " air-drying oven," the muscle may 
be dried on an evaporating dish or sand bath on the stove. 

41. Put the dry muscle in a porcelain or platinum 
crucible, and heat it until the muscle is reduced to ashes. 



54 THE MUSCULAR SYSTEM. 

Let the ashes cool, then weigh them. The weight of the 
ashes represents the amonnt of mineral in the muscle. What 
per cent of the muscle is mineral matter ? 

42. Dissolve the ashes in water, divide the solution into 
five parts, and test the respective portions for potassium, 
sodium, calcium, phosphates, carbonates, and chloride. (See 
Appendix.) Which of these substances gives the greatest 
amount of precipitates ? 

43. Soak fifteen or twenty grains of muscle in tepid 
water for four hours. Filter the solution, and test a portion 
for lactic acid (sarcolactic acid). (See " Tests " in Ap- 
pendix. ) 

44. Take a dead muscle, remove all fat and tendons, and 
wash it in water until the washings give no trace of proteids ; 
mince thoroughly, and treat with a ten-per-cent solution of 
common salt (ammonium or magnesium chloride may be 
used in place of the common salt), which dissolves out a 
viscid fluid. Filter the viscid liquid, and as it passes through 
the filter, let it drop into distilled water, in which it forms 
a white, fleecy precipitate (myosin). 

See if the viscid fluid will dissolve in a ten-per-cent solu- 
tion of common salt; in dilute muriatic (hydrochloric) acid; 
in picric acid or tincture of guaiacum. What color does it 
give in the last case? Is myosin a proteid ? Test it for 
proteids. 

THE MUSCULAR SYSTEM TEXT. 

The " Master Tissues." — The muscles and nerves have 
been very appropriately called the master tissues. Not only 
on account of the functions they perform, but also from the 
fact that most of the other tissues work to support these 
tissues. Note as we proceed in our study how and why this 
is the case. 

Motion Essential to Our Being. — Food must be secured, 
digested, taken to the blood, the blood taken to the tissues, 
and then the blood returned to the excretory organs that the 
waste products may be removed. These, with the various 
other acts of the body, require motion. 1 In the amoeba we 
found that the power of motion was equally distributed to 



^Mechanism of Motion.— Many of the movements of the body are produced in 
the same way as in many forms of machinery,— by means of levers or a system 
of levers. 



MUSCULAR SYSTEM. 55 

all parts of the body. In the higher animals, however, the 
work of motion is confined to one tissue, called the contractile 
or muscular tissue, which has the power of shortening, or con- 
tracting, and returning to its first condition , relaxing, and 
being attached to firmer parts, motion is produced. In most 
of the movements of the body the muscles are attached to 
firmer parts (bones), which act as levers, this making pos- 
sible locomotion and various other movements. There are 
some few movements that take place in the body which are 
not dependent on muscles, as the movement produced by cil- 
iated cells, and the migration of white corpuscles. 

The Muscular System. — The muscles of the body make 
up what is called the flesh. The muscles, which are attached 
to the skeleton of the body, and by which its voluntary move- 
ments are produced, are called skeletal muscles. 



A lever is an inflexible bar, free to move about a point called the fulcrum. 
The resistance to be overcome is called the weight, and the force acting to over- 
come or balance this resistance is called the power. From the relation which 
these parts bear to each other, levers are of three classes. When the fulcrum is 
between the weight and the power, the lever is of the first class; when the 
weight is between the power and the fulcrum, the lever is of the second class; 
and when the power is between the fulcrum and the weight, the lever is of the 
third class. 

If the power applied is less than the resistance overcome, there is a gain of 
intensity; if the point to which the power is attached moves slower than the point 
to which the weight is attached, there is a gain of velocity. Intensity is the 
advantage sought in levers of the first and second class and velocity in 
the third-class lever; but in some instances, velocity is the advantage sought in 
the first-class lever, as in the hamstring muscle inserted to the tuberosity of the 
ischium, and originating from the posterior part of the knee joint, in which the 
muscle attached to the ischium is the power, the hip joint the fulcrum, and the 
trunk and head the weight. This muscle raises the body erect when bent for- 
ward. We have a good example of a second-class lever in the jaw; the jawbone 
being the lever, its articulation at the temporal bone the fulcrum, the masseter 
muscle the weight, and the genio-hyoid inserted to the interior of the tip of the 
ch^n the power. The forearm is a third-class lever; the ulna being the lever, the 
elbow joint the fulcrum the biceps muscle the power, and the hand and the 
object to be lifted are the weight. 

By being of the third-class the forearm has greater freedom and speed of 
movement, and while there is a great loss of intensity, this is more than made up 
in the grace and velocity of the movements of the arm. The foot gives us an 
example of the three classes of levers: extending the foot, first-class; second- 
class when the body is raised on tiptoe; and the flexion of the foot, third-class. 

Prove the statement in regard to the foot by determining the position of the 
fulcrum, power, and weight in each of the cases mentioned. 



PEI^CIPAL MUSCLES. 

(See Plates II, III, IV, V, and VI.) 



MUSCLE. 


ORIGIN. 


INSERTION. 


FUNCTION. 


Occipito-frontalis. 


Superior curved 


T o muscles o f 


Moves the scalp, 




line of occipital 


eyelid and apo- 


gives expression 




bone and angular 


neurosis in front. 


of surprise, and 




process of frontal 




when much con- 




bone. 




tracted that of 
fright or horror. 


Orbicularis palpe- 


Internal margin 


Outer margin of 


Closes the eye- 


brarum. 


of orbit. 


orbit. 


lids. 


Levator palpebra- 


Lesser wing of 


Upper tarsal car- 


Lifts upper eye- 


rum. 


sphenoid. 


tilage. 


lid. 


Corrugator super- 


Superciliary ridge 


Under surface of 


Pulls eyebrow 


cilii. 


of frontal bone. 


orbicularis palpe- 


downward and in- 






brarum. 


ward ; it is the 
"frowning " mus- 
cle and principal 
one in expression 
of suffering. 


Levator labii su- 


Nasal process of 


Alar cartilage of 


Draws the wing 


periors a 1 se q ue 


superior maxil- 


nose and to the 


of nose and upper 


nasi. 


lary bone. 


upper lip. 


lip upward. Chief 
muscle of nose. 
Chief muscles in 
expression of con- 
tempt and d i s - 
dain 


Dilator naris an- 


Alar cartilage. 


Border of wing 


Dilates nostrils. 


terior. 




(ala) of nose. 




Dilator posterior. 


Nasal notch of 


Skin at margin of 


Dilates nostrils ; 




superior maxil- 


nose. 


active in difficult 




lary bone. 




breathing. Con- 
tracted in expres- 
sion of anger. 


Zygomaticus ma- 


Malar bone. 


Angle of the 


Angle of mouth 


jor. 




mouth. 


backward and up- 
ward, as in laugh- 
ing. 


Zygomaticus mi- 


Malar bone. 


Outer part of up- 


Draws upper lip 


nor. 




per lip. 


backward, up- 
ward, and out- 
ward. Gives to 
the face expres- 
sion of sadness. 


Levator labii in- 


Incisive fossa of 


Skin of lower lip 


Raises and pro- 


ferioris. 


inferior maxil- 


and the chin. 


trudes the lower 




lary. 




lip, and wrinkles 
the skin of the 
chin. Gives ex- 
pression of doubt 
or disdain. 


Depressor labii 


External oblique 


Angle of mouth. 


Lip directly down- 


inferioris. 


line of inferior 




war d and out- 




maxillary. 




ward. Gives ex- 
pression of irony. 


Orbicularis oris. 1 


Nasal septum, ca- 


Forms lips and 


Closes the mouth. 




nine fossa of in- 


sphincter of the 






ferior maxillary, 


mouth. 






and by accessory 








fibers from other 








muscles. 







i The orbicularis oris is not a true sphincter muscle, but consists of numer- 
ous layers of muscular fibers having various directions. From these fibers are 
derived various of the facial muscles, as the buccinator, levator, and depressor 
anguli oris, the levator labii, zygomatic!, and depressor labii. 



PRINCIPAL MUSCLES. 



57 



MUSCLE. 


ORIGIN. 


INSERTION". 


FUNCTION. 


Buccinator. 


From alveolar 


Orbicularis oris. 


Contracts and 




process o f infe- 




compresses the 




rior and superior 




cheek ; keeps food 




maxillary bones 




under pressure of 




and pterygo-max- 




the teeth. 




illary ligament. 






Risorius. 


From fascia over 


Skin at angle of 


Retracts angle of 




the masseter mus- 


mouth. 


the mouth, as in 




cle. 




smiling. Called 
the " smiling " 
muscle. 


Temporal 


Temporal fossa 


Coronoid process 


Raises and re- 




and fascia. 


of inferior maxil- 


tracts the lower 






lary. 


jaw. 


Masseter. 


Zvcomaric arch 


Ansrle and ramus 


With the pterv- 




and malar proc- 


of jaw. 


goid, moves the 




ess superior max- 




lower jaw for- 




illary. 




ward on the up- 
per ; deep fibers 
the jaw backward. 


External ptery- 


Pterygoid plate 


Neck of condyle 


Chief agent in 


goid. 


and greater wing 


of lower jaw. 


trituration of the 




of the sphenoid. 




food. Moves the 
lower jaw for- 
ward. 



NECK. 



riatysma myoi- 


Clavicle, acromion 


Inferior maxillary 


Depresses the jaw. 


dcs. 


process of scapula 


and angle of 


Draws lip and 




and fascia. 


mouth. 


mouth down. 
Gives expression 
of melancholy. 


Sterno-mastoid. 


By two heads, 


Mastoid process 


Depresses and ro- 




sternum and clav- 
icle 


of temporal bone. 


tates the head. 


Sterno-hyoid. 


Sternum and 


Hyoid bone. 


Depresses larynx 




clavicle. 




and hyoid after 
they have been 
drawn up in de- 
glutition. 


Sterno-thyroid. 


Sternum and car- 


Side of thyroid 


Depresses the lar- 




tilage of first rib. 


cartilage. 


ynx. 


Stylo-glossus. 


Styloid process of 


Side of tongue. 


Elevates and re- 




temporal bone. 




tracts the tongue. 


Digastric. 


Anterior body 


Hyoid bone. 


Raises hyoid bone 




from inner sur- 




i n deglutition ; 




face of inferior 




hyoid fixed de- 




maxillary ; poste- 




presses jaw. 




rior body, groove 








of mastoid proc- 








ess. 






G e n i o - h y o - 


Superior genial 


Hyoid bone and 


Posterior fibers of 


glossus. 


tubercle of infe- 


inferior surface of 


tongue forward : 




rior maxillary. 


tongue. 


anterior fibers of 
toncrue back. Both 
muscles acting 
make tongue con- 
cave. 


Hyo-glossus. 


Cornu of hyoid 


Side of tongue. 


Makes tongue 




bone. 




convex. 


Stylo-pharyngeus. 


Styloid process. 


Thyroid cartilage. 


Elevates the phar- 
ynx. 



58 



PRINCIPAL MUSCLES. 



MUSCLE. 


ORIGIN. 


INSERTION. 


FUNCTION. 


Constrictors. 


Inf. cricoid and 


Raphe of phar- 


Lessens the cali- 




thyroid cart. Mid. 


ynx. 


ber of the phar- 




cornu of hyoid 




ynx. 




and stylo-hvoid 








lig. Sup. inter- 








pterygoid plate 








jaw and side of 








tongue. 






Rectus capitis an- 


Transverse proc- 


Basilar process of 


Flexes the head 


ticus major. 


ess and lat. mass 


occipital bone. 


and slightly ro- 




of atlas. 




tates it. 


Scaleni. 


Anterior tubercle 


Trans, process of 


When fixed above 




of first rib. Mid- 


third to sixth cer- 


elevate first and 




dle of first rib. 


vical vertebrae. 


second rib. 



TRUNK. 



Trapezius. 



Latissimus dorsi. 



Serrati. 



Complexus. 



Erector spinse. 



Longissimus dor- 
si. 



Intercostals, ex- 
ternal. 1 



Intercostals, in- 
ternal. 



Superior curved 
line of occipital 
bone, spinal proc- 
ess of last cervi- 
cal vertebrae, all 
dorsal vertebrae. 
Spines of six 
lower dorsal ver- 
tebrae and lumbar 
and sacral verte- 
brae, crest of il- 
eum and three or 
four lower ribs. 



Margin 8 upper 
ribs. Posterior 
spine of last 2 
dorsal, first 3 
lumbar ; superior 
spine of 7th cer- 
vical, 2 upper 
dorsal. 

Trans, process 7th 
cervical, 6 upper 
dorsal, articular 
process of 3d to 
6th cervical. 

Crest of ilium, 
sacrum, lumbar, 
3 lower dorsal 
spines. 

From erector spi- 
nse. 



Outer lip of the 
inferior border of 
ribs. 

Inner lip of the 
inferior border of 
ribs. 



Clavicle, spine of 
scapula and acro- 
mion process. 



Bicipital groove 
of humerus. 



Posterior border 
of scapula. Four 
lower ribs. 2d, 
3d, 4th, and 5th 
ribs. 



Occipital bone. 



Divides into sac- 
ro-lumbalis, lon- 
gissimus dorsi 
and spinalis 
dorsi. 

Transverse proc- 
ess of lumbar and 
dorsal vertebrae, 
7th to 11th ribs. 
Superior border 
of ribs above. 



Superior border 
of ribs below. 



Elevates the 
shoulder, as in 
s u p p o rting a 
weight. Draws 
head backward. 

Aids in giving 
downward blqw, 
as in chopping ; 
when arm is fixed, 
aids in raising 
the ribs ; when 
both arms fixed, 
draws the whole 
body forward. 
Elevate the ribs. 
Depress the ribs. 
Raise the ribs. 



Holds head erect. 



Extension of lum- 
bar spines on pel- 
vis. 



Erects the spines 
and bends the 
trunk backward. 

Raise the ribs in 
inspiration. 

Depress the ribs 
in expiration. 



i The view given here of the function of the intercostals is that of Hutchin- 
son. This action is, however, disputed by a number of eminent anatomists, as 
Haller, who thinks they " act in common." 

The. first theory is the one generally taught in this country, while the theory 
of Haller has many followers in Europe, and has the support of many observa- 
tions, both in disease and health. 



PRINCIPAL MUSCLES. 



59 



Ml'SCLE. 


ORIGIN. 


INSERTION. 


FUNCTION. 


Diaphragm. 


Tip of sternum, 
six or seven lower 
ribs, from behind 
by two upon 
a p o n e u - 
rotic notches and 
bodies of lumbar 
vertebra?. 


Central tendon. 


Principal muscle 
o f inspiration. 
Used also in ex- 
pulsive acts. 


Obliquus exter- 
nus. 


Eight lower ribs. 


Median line(linea 
alba). Crest of 
ilium, Poupart's 
ligament. 


Compresses the 
viscera and flexes 
the thorax. An 
expiratory muscle. 


Obliquus Interims. 


Lumbar fascia, 
crest of ilium, 
Poupart's 1 i g a - 
ment. 


Three lower ribs, 
linea alba, pubic 
crest, pectineal 
line. 


Compresses the 
viscera, flexes the 
thorax, aids in 
expiration. 


Rectus abdominis. 


Crest of pubic 
bone. 


To the cartilages 
of the 5th and Gth 
ribs. 


Compresses the 
viscera and flexes 
the thorax. 



UPPER EXTREMITY. 



Pectoralis major. 

Pectoralis minor. 
Deltoid. 

Subscapularis. 
Coraco-brachialis. 



Biceps flexor cu- 
biti. 



Brachialis a n t i- 
cus. 

Triceps extensor 
cubiti. 



Pronator quadra- 
tus. 

Pronator radii 
teres. 



Flexor carpi ul- 
naris. 



Sternal half of 
clavicle, sternum, 
and cartilage, 6th 
or 7th rib. 

Third, fourth, and 
fifth ribs. 
Clavicle, acro- 
mion, and spine 
of scapula. 

External surface 
of scapula. 



Coracoid process 
of scapula. 



Long head, gle- 
noid cavity ; short 
head, coracoid 
process. 

Lower half of the 
shaft of the hu- 
merus. 

Exter. and inter, 
heads near mus- 
culo-spiral groove 
of shaft of hu- 
merus : long head 
from glenoid cav- 
ity. 

Lower fourth of 
ulna. 

Internal condyle 
of humerus and 
coronoid process 
of ulna. 

1st head, internal 
condyle of humer- 
us : 2d head olec- 
ranon of radius 
and from ulna. 



External bicipital 
ridge of humerus. 



Coracoid process 
of scapula. 
Prominence o n 
the middle of the 
outer half oft shaft 
of humerus. 
Lesser tuberosity 
of the humerus. 



To a ridge on 
middle of inner 
surface of hu- 
merus. 

Tuberosity of the 
radius. 



Coronoid process 
of ulna. 



Olecranon process 
of ulna. 



Lower fourth of 
the shaft of ra- 
dius. 

Outer side of 
shaft of radius. 



Annular liga- 
ment, pisiform 
bone, and 5th 
metacarpal. 



Depresses the 
arm when raised 
by the deltoid. 
Draws the arm 
forward. 

Depresses point 
of the shoulder. 
Raises the arm 
directly from the 
side. Abducts the 
humerus. 

Rotates head of 
humerus inward 
and aids, by its 
tone, in prevent- 
ing displacement 
of humerus. 
Moves humerus 
forward and in- 
ward. 



Flexes and supl- 
nates forearm. 



Flexes arm and 
protects elbow 
joint. 

Extends the fore- 
arm. Protects the 
under part of the 
shoulder joint. 



Pronates the hand. 



Pronatesthe hand 
and aids in flexing 
forearm. 

Flexes the wrist. 



60 



PRINCIPAL MUSCLES. 



MUSCLE. 


ORIGIN. 


INSERTION. 


FUNCTION. 


Flexor profundus 


Shaft of ulna. 


Last phalanges 


Flexes the pha- 


digitorum. 




by four tendons. 


langes. 


Flexor sublimis 


1st head, inner 


Second phalanges 


Flexes second 


digitorum. 


condyle of burner 
us ; 2d head, coro- 
noid process of 
ulna ; 3d head, 
oblique line of ra- 
dius. 


by four tendons. 


phalanges. 


Flexor longus pol- 


Shaft of radius. 


Last phalanx of 


Flexes last pha- 


licis. 




thumb. 


lanx of thumb. 


Palmaris longus. 


Internal condyle 


Annular ligament 


Tensor of the pal- 




of humerus. 


and palmar fas- 


mar fascia, and 






cia. 


assists in flexing 
wrist and elbow. 


Supinator longus. 


External condy- 


Styloid process of 


Flexor and supi- 




loid ridge of the 


radius. 


nator of forearm. 




humerus. 






Extensor carpi ul- 


1st head, exter- 


Base of 5th meta- 


Extends wrist. 


naris. 


nal condyle hu- 
merus ; 2d head, 
posterior border 
of ulna. 


carpal bone. 




Extensor carpi 


Lower third of 


Base of 3d meta- 


Extends wrist. 


radialis. 


external c o n d y- 
loid ridge of hu- 
merus. 


carpal bone. 




Extensor commu- 


External condyle 


All of the 2d and 


Extends the fin- 


nis digitorum,. 


of humerus. 


3d phalanges. 


gers. 


Extensor minimi 


External condyle 


2d and 3d phalan- 


Extensor of little 


digiti. 


of humerus. 


ges of little finger. 


finger. 


Extensor o s s i s 


Posterior surface 
of shaft of the ul- 


Base of metacar- 


Extends the 


metacarpi polli- 


pal bone of 


thumb. 


cis. 


na and the radius. 


thumb. 




Extensor indicis. 


Posterior surface 


2d and 3d phalan- 


Extends index fin- 




of shaft of ulna. 


ges of index finger. 


ger. 


Interossei, palmar 


From the sides of 


From the aponeu- 


A d d u c t index, 


(3). 


metacarpal bones. 


rosis of extensor 


ring, and little 






tendons. 


fingers. 


Interossei, dorsal 


From the five 


Sides of the apo- 


Abduct index, 


(4). 


metacarpal bones. 


neurosis of exten- 


middle, and ring 






sor communis. 


fingers. 



LOWER EXTREMITY. 



Psoas magnus. 


Bodies and trans- 


Lesser trochanter. 


Flexes and rotates 




verse processes of 




the thigh out- 




last dorsal, all 




ward ; flexes trunk 




lumbar vertebras. 




on pelvis. Assists 
in keeping erect 
position by sup- 
porting spine and 
pelvis on femur. 


Iliacus. 


Iliac fossa, crest, 


Lesser trochanter, 


Acting with psoas 




base of the sa- 


oblique line of fe- 


magnus, flexes 




crum. 


mur to linea as- 


thigh and rotates 






pera. 


femur outward. 


Tensor vaginae fe- 


Outer lip of crest 


Fascia lata, outer 


Tensor of fascia 


moris. 


of ilium ; anterior 


side of thigh. 


lata, also abducts 




superior spinous 




and rotates thigh 




process of ilium. 




inward. 



PRINCIPAL MUSCLES. 



61 



Sartorius. 1 



Quadriceps exten- 



Pectineus. 

Adductor magnus. 

Adductor longus. 
Gracilis. 

Gluteus maximus. 



Biceps 3 (flexor 

cruris) . Acts with 

Semitendinosus 

and Semimembri- 

nosus. 

Tibialis anticus. 



Extensor longus 
digitorum. 



Extensor proprius 
hallucis. 



ORIGIN. 



Anterior superior 
process of ilium 
and upper half of 
notch below. 



Vastus, external, 
anterior border of 
greater trochan- 
ter and linea as- 
pera : vastus, in- 
ternal, lip of 
linea aspera. Rec- 
tus femoris ante- 
rior inferior spine 
of ilium, edge of 
acetabulum. 
Ilio-pectineal line 
of innominataand 
pubes : fascia of 
anterior surface 
of muscle. 
Descending: ramus 
of os pubis and 
ascending ramus 
and tuberosity of 
ischium. 
Front of os pubis. 

Symphasis and 
ramus of os pu 
bis. 



Gluteal line and 
crest of ilium, sa- 
crum, and coccyx. 



Long head from 
tuberosity of is- 
chium : short 
head from linea 
aspera. outer lip. 
Outer tuberosity, 
upper part of 
shaft of tibia. 

Outer tuberosity 
of tibia and upper 
part of shaft of 
fibula. 

From interosseous 
membrane and 
middle part, an- 
terior surface of 
fibula. 



INSERTION. 



F p p e r internal 
surface of shaft 
of the tibia by U- 
shaped aponeuro- 
sis. 



Tuberosity of tibia 
border of patella. 
Common tendon 
contains the pa- 
tella. 



Femur below les- 
ser trochanter. 



Linea aspera of 
femur. 



Linea aspera, 
middle part. 
Upper part to in- 
ner surface of 
shaft and lower 
part to inner tu- 
berosity of tibia. 
Greater trochan- 
ter and fascia 
lata and linea as- 
pera of femur. 



Head of fibula 
and external tu- 
berosity of tibia. 



Internal cunei- 
form bone and 
metatarsal bone 
of great toe. 
Second and third 
phalanges of toes. 



Last phalanx of 
great toe. 



FUNCTION. 



Flexes the leg on 
the thigh, and its 
continued action 
flexes thigh, the 
pelvis ; next r o - 
tates thigh out- 
ward. 

Extends leg upon 
thigh. Rectus as- 
sists psoas and 
iliacus in sup- 
porting pelvis 
and trunk upon 
the femur or in 
bending It for- 
ward, 



Adducts thigh; 
flexes thigh and 
rotates it out- 
ward. 

Adducts the thigh 
and rotates it 
outward. 



Adducts and 
flexes the thigh. 
With sartorius 
flexes the leg and 
rotates it inward. 
It also adducts 
the thigh. 
Keeps trunk in 
erect position. Ex- 
tends and rotates 
thigh outward. 
Enables the body 
to regain erect 
position after 
stooping. 

Flexes the leg on 
the thigh and ro- 
tates the leg out- 
ward. 

Flexes tarsus 
upon leg. 



Extends the toes. 



Extends the great 
toe. 



i The sartorius does not adduct the leg, as was formerly supposed, so that 
the name " tailor muscle " is inappropriate. 

2 This is the great extensor muscle of the leg, and divides into four por- 
tions, named respectively, rectus femoris, vastus externus, vastus interims, and the 
crurew*. 

3 The biceps, semitendinosus, and semimembrlnosus are called the "ham- 
string muscles." The hamstring tendon is composed of the tendons of the three 
muscles just mentioned with that of the gracilis. 



62 



THE MUSCULAR SYSTEM. 



MUSCLE. 


ORIGIN. 


INSERTION. 


FUNCTION. 


Gastrocnemius. 


Inner head from 


Tendo Achillis. 


Extends the foot. 




inner condyle and 




Used in standing. 




outer head from 




leaping, and 




external condyle 




walking. 




of femur. 






Soleus. , 


Back part of head 


Os calcis by tendo 


Extends the foot. 




of fibula, oblique 


Achillis. 






line, and internal 








line of tibia. 






Plantaris. 


Linea aspera and 


Os calcis by tendo 


Accessory to gas- 




ligament of knee 


Achillis. 


trocnemius. 




joint. 






Popliteus. 


External condyle 


Shaft of tibia. 


Aids in flexing 




of femur, poste- 




leg on thigh. Leg 




rior ligament of 




flexed, rotates leg 




knee joint. 




inward. 


Interossei, dorsal. 


Adjacent surface 


Base of first pha- 


Abduct from the 




of metatarsal 


langes. 


middle of the sec- 




bones. 




ond toe. 


Interossei, plan- 


Inner lower sur- 


Base of first pha- 


Adducts the outer 


tar. 


face of three 


langes of three 


three toes. 




outer metatarsal 


outer toes. 






bones. 







Motion, however, is needed in other parts as well as in 
the skeleton, for respiration, circulation, digestion, and other 
functions. Muscular tissue is therefore found in the larynx, 
the trachea, the bronchial tubes and their branches, the 
tongue, the alimentary canal, the arteries, the veins, the 
heart, and in some other parts of the body. 

Skeletal Muscles. — The typical skeletal muscle is more 
or less fusiform in shape, and consists of an expanded fleshy 
portion, the body (Fig. 48), and a flat or narrow portion 
{tendons) composed of white inelastic tissue, by which it is 
attached to the bone or to other muscles. If we should 
examine the body, however, we would find the muscles differ- 
ing very much in shape and size. Some of the more .impor- 
tant forms are shown in Fig. 34. When a muscle has the 
tendons at the side, and the fibers arranged along it, like the 
vane of a feather, it is called penniform; when the fibers 
are on both sides of the tendon, bipenniform; with the ten- 
don at the end, the fibers radiate — are fan-shaped; consist- 
ing of an expanded portion, and ending in a tendon above 
and below, fusiform, or spindle-shaped; when it originates 
from two tendons, a biceps; when from three tendons, a tri- 
ceps; consisting of two bodies with an intervening tendon, 
digastric; made up of circular fibers, so as to form a mus- 
cular ring, sphincter. 



STRUCTURE OF MUSCLES. 



63 



From the specimen you have for dissection, see how many 
of these forms you can select. 

Arrangement of Muscles. — From the dissection of a rab- 
bit we may learn that the muscles are arranged into two or 
more well-marked layers, bound together by a common sheath 
(fascia) of connective tissue. Those near the surface are 
known as superficial muscles ; those near the bone as deep- 
seated muscles. 

Number of Muscles. — There are more than fixe hundred 
muscles in the human body, each of which 
has its respective name and function, and 
by the separate or combined action of these 
the various movements of the body are pro- 
duced. 

We cannot, in our brief study of the sub- 
ject, learn the names and action of all these 
muscles, but a study of them in connection 
with Figs. 35 to 47, Plates II to VI, and the 
diagram of the principal muscles, will help us 
in understanding the use of some of the more 
important muscles of the body. 

The movements of our body differ very 
much in the number of muscles they call into fig. 48.- typical 

IYIttspt td 1 Ten- 

action; to illustrate, try Experiment 23. don . 2. Body. 

Structure of Muscles. — Let us now examine more thor- 
oughly some of the muscles. Let us take the biceps muscle 
of the arm. We have noticed that a muscle generally con- 
sists of two parts, — the fleshy portion, or the contractile 
part, and the tendon, or the inelastic part. The tendons are 
composed of white, inelastic fibrous tissue, and are generally 
very strong. This gives the muscles a firm attachment, so 
that the entire contraction will be effective in producing 
motion. What difference would there be if the tendons were 
elastic ? 

The tendons are attached to the coverings of the bones 
(periosteum) directly or indirectly by means of other tendons 
which are attached to the periosteum. The tendons are most 




64 THE MUSCULAR SYSTEM. 

numerous near the large joints, where they permit free 
motion, and yet occupy little space. 

What inconvenience would there be in having the larger 
muscles cover the joints ? 

Grasp your arm near the elbow, and bend it forcibly, 
and you can feel the tense tendon of the biceps as it is drawn 
by the muscle to move the forearm. The tendons may be 
easily noticed in the back of the hand. The wonderful dex- 
terity and flexibility of the hand is due for the greater part 
to the numerous tendons of the palm and back of the hand, 
and to the fact that the muscles which move them are located 
in the arm. The strongest and largest tendon of the body 
connects the larger muscles of the calf of the leg to the heel 
bone (os calcis). It is called the tendon of Achilles. 

From what we have seen, we learn that when the muscle 
contracts, it pulls on the tendons, which transfer the motion 
to the bones to which they "are attached. 

From our dissection we have learned that tendons are 
variously situated at each end of the muscle, as in the muscle 
which bends the arm, — in the middle of the muscle, its 
fibers running obliquely from it, looking like the quill of a 
feather; or they may spread out into membranes, as in the 
tendons of the occipito frontalis, when they are known as an 
aponeurosis; or they may have a tendon in the middle, as 
well as at each end, as in the digastric muscle of the jaw. 

There are numerous places in the body where muscles 
have to glide over prominences or pass through grooves; if 
there were not such special provision, their movement over 
these parts would cause undue friction and heat. This is 
prevented by these parts having a special membrane, which 
covers or lines the part, secreting a fluid that renders the 
movement easy. These membranes are called synovial mem- 
branes. 

The tendon attached to the part that is fixed is called 
the origin; the one attached to the part that moves, the inser- 
tion. Determine and examine the origin of some of the more 
important muscles mentioned in the list. To what part of 
a machine does the tendon correspond ? 



STRUCTURE OF MUSCLES. 



65 



Gross Structure of the Muscle. — Let us return to the 
study of the body of a muscle. Observe that it is covered 
by a sheath of connective tissue (epimysium) (Fig. 13). 
On examination of a transverse section of the muscle we find 
that it is not a solid piece of muscular substance, but made up 
of a great many parts, some of which are almost microscopic 
in size, and they are separated from each other by partitions 
of connective tissue (perimysium). From dissecting out 
some of the smaller bundles, and examining them with the 

microscope, we fiud that they 
are made up of smaller bundles, 
and that the smaller bundles 




Fig. 49. A.— Muscular Fiber from 

Beetle (Hydrophilus piceus). 

a. Substance of muscle, d. Cross 

strire. c. Doyere's prominence, b. 

Entering of nerve fiber. (Sanderson). 



Fig. 49. B. — Transverse Section of 
Muscle Fiber from Tongue of Cat. 
1. Muscle fiber. 2. "Cobnbeim's areas." 
(Brinckley. 0. W. B.) 



(fasciculi) have a delicate sheath (endomysium), and that 
they are made up of delicate thread-like bodies (muscle 
fibers). 

Microscopic Structure of Muscles. — Skeletal Muscles. — 
Let us now examine the individual muscular fiber (Fig. 
14), for it is the difference in their structure that gives to 
the three classes of muscles their respective properties. The 
skeletal-muscle fiber is on the average one five-hundredth of 
an inch in diameter, and a little over an inch in length. It is 
cylindrical in form, and presents numerous transverse mark- 



66 THE MUSCULAR SYSTEM. 

ings. Each fiber has a transparent, elastic sheath called the 
sarcolemma. 

We have learned from our experiment that muscles are 
often arranged in pairs. The muscles which act in opposi- 
tion to each other, as the biceps and triceps of the arm, are 
called antagonists. 

Were it not for such muscles our movements would be 
slow, and in many cases impossible. Suppose there were only- 
muscles to bend the limbs, can you think of any inconvenience 
that would arise ? Try the experiment. What do you learn ? 

Names of Movements. — Perform the following move- 
ments, and notice what muscles are brought into action : Bend 
(flex) the arm, straighten out (extend) the arm; draw the 
arm away (abduct) from the body; bring it to (adduct) the 
body; turn the hand (pronate) so that the palm will be down ; 
turn the hand (swpinate) so as to have the palm up. Do 
you find different muscles for each of these movements ? 

Kinds of Muscles as to Function. — 'Muscles which bend 
the limbs are called flexors; those which straighten the limbs, 
extensors; those which draw parts away from the body, 
abductors; to the body, adductors; those which lift parts, as 
the eyelid or corner of the mouth, levators ; that draw parts 
down, depressors; those that turn the palm of the hand up, 
supinators; the palm down, pronators. 

How Muscles Are Named. — Muscles are named in vari- 
ous ways: from their form, trapezius; their position, latis- 
simus dor si; their size, serratus magnus; their origin, biceps 
flexori cubiti; or their function, levator anguli oris. (See 
Glossary.) 

The muscle fiber is composed of contractile protoplasm. 
Under very high power its structure is seen to be very com- 
plex, more complex than we can here consider ; but it is neces- 
sary that we study some of its more important features. 

The contractile substance is marked by alternate dim 
and light stripes (Fig. 49) running across the fiber, which 
has given to them the name of striped, or striated, muscles. 1 

ilf a transverse section of a muscle fiber is examined under high power, it is 
seen to be subdivided into smaller areas (Fig. 49) (the areas of CoJinheim), which 



INVOLUNTARY MUSCLES. 67 

Plain Muscular Tissue. — Involuntary, or plain, mus- 
cular tissue is composed of spindle-shaped cells (Fig. 15) 
about one five-hundredth of an inch in length and about one 
eighth as wide. It has one or more prominent nuclei, which 
are oval, and exhibit intranuclear network, and one or more 
nucleoli. 

The cell substance presents a longitudinal, but no trans- 
verse, striation, and each cell seems to have a delicate sheath. 
The cells have between them a small quantity of cementing 
substance. These are collected together in bundles covered 
by connective tissue. Along this connective tissue the blood 
vessels pass, and from these capillaries go to the individual 
fibers. (Where found, see below.) 

Heart Muscle. — While the heart is an involuntary muscle, 
it is quite different from the plain involuntary muscle tissue. 
Its fibers, like those of the skeletal muscle, present transverse 
marks (Fig. 16), or striae. Its fibers, however, are smaller 
than those of the skeletal muscles, and are made up of oblong- 
shaped cells having a prominent nucleus near its center, and 
with one or more nuclei, and whose cells sometimes give off 
branches to other cells. The cells are without an investing 
sheath. These cells have an abundant supply of blood vessels 
and lymphatics. 

Distribution of Plain Muscle Tissue This tissue is 

found in the alimentary canal below the middle of the esoph- 
agus; in the trachea and bronchi; in the air cells in the 
middle coat of the arteries, and in some veins ; in the larger 
lymphatics; in the bladder and ureters; in the ducts of 
glands in the iris and ciliary muscles, and in the true skin, 
especially between the bases of the papilla?. 

represent the muscle columns of which the fiber is composed. After death, or on 
being hardened in alcohol, chromic acid, and certain other reagents, it presents 
a well-defined longitudinal marking, and may be easily split up into smaller 
threads, or fibrillae, which correspond to the muscle columns (sarcostyles) of the 
living muscle. By treating the muscles with certain reagents, they may be split 
up into transverse disks. From this we learn that the fibers are composed of a 
mass of fibrils {sarcostyles) imbedded in interfibrillar substance (sarcoplasm) , and 
composed of alternate segments of dim and clear substance. It is these muscle 
columns which are the actual contractile elements of the muscle. Just beneath 
the sarcolemma will be seen numerous dots, or nuclei, which under high power 
appear nucleated and imbedded, or surrounded by a variable amount of proto- 
plasm. A nucleus with its surrounding protoplasm is called a muscle corpuscle. 



68 



THE MUSCULAR SYSTEM. 



Blood Vessels of Muscular Tissue. — On account of the 
large amount of work the muscles have to do, they need an 
abundant supply of blood, not only to furnish material to 
supply the constant exercise of energy, but to carry away the 
waste products of their action as well. 

When we study their structure, we see how admirably 

this demand has been 
met. Not only does the 
connective tissue bind 
the various parts of the 
muscle together, giving 
it support, but it also 
serves as the means by 
which the blood vessels 
and nerves are distrib- 
uted to the various parts 
of the muscle. 

The arteries, accom- 
panied by the veins, en- 
ter at various points, 
branch into the connec- 
tive tissue (areolar) be- 
tween the fasciculi, and 
finally terminate in 
capillaries that form 
an oblong network 

.Arteriole. I ab *n (*% 60 ) ^^ <** 

them. (After Sanderson.) fibers Outside of the 

sarcolemma. These capillaries are very small, and from 
them exudes the fluid by which the muscle fiber is nour- 
ished. 

It is also in the connective tissue that the lymph spaces, 
that make the beginning of lymphatic vessels, are formed, so 
that each fiber is surrounded by a capillary blood vessel and 
a lymph space, the lymph acting as a medium of exchange 
between the blood and the muscle tissue in a way that will be 
explained when we study the lymph. 




Fig. 50.- 



Section of an Injected Muscle 
of a Eat. 



MUSCULAR ACTION. 69 

Nerves of Muscle Tissue. — It is from the nerves that the 
muscle receives its normal stimulus ; it is essential that it be 
well supplied with them. This we find to be the case. The 
nerve fibers, chiefly medullated, are from the central nervous 
system. The nerves branch in the connective tissue, first 
forming plexuses, and then divide until a single nerve fiber 
enters each muscular fiber, the primitive sheath of the nerve 
fiber fusing with the sarcolemma ; while the axis cylinder of 
the nerve passes through it, and ends in a terminal ramifica- 
tion called an end plate, on the substance of the fiber (Fig. 
51). Each fiber appears to receive one end plate about its 
middle, and so distributed that a nervous impulse along the 
different fibers going to the muscle reaches the different parts 
about the same time, and thus produces a simultaneous con- 
traction in the organ. 

Involuntary muscles are supplied with nonmedullated 
nerve fibers derived from the sympathetic system. In some 
cases they e*id in knot-like processes. 

Muscular Contraction. — One of the most characteristic 
properties of living animals is the power to produce spon- 
taneous movement. It may be simple, as the protruding or 
flowing out of the body substances, and exercised by any part 
of the body, as in the movement of the amoeba, or it may be 
more complex and restricted to a particular part or tissue 
of the animal. In the higher animals the power of produc- 
ing motion by contraction is restricted to a single tissue, the 
muscular tissue. 

By experiment with a muscle-nerve preparation (Fig. 
33), we may learn of the mode and nature of muscular con- 
traction. 

By stretching the muscle it is found to be elastic, while 
slight, yet it is perfect in returning to its exact length when 
the force is removed. 

By the application of the electric current a muscle may 
be made to contract, or shorten. Similar effects may be pro- 
duced by heat, certain chemicals, or by a blow upon it. 
Those agents which cause the muscle to contract are called 



70 



THE MUSCULAR SYSTEM. 



stimuli, and the property of responding to stimuli is called 
irritability. The stimulus may be applied to the nerve going 
to the muscle or to the muscular tissue direct. The mus- 
cles, when at rest, are normally slightly contracted, keep- 
ing them on a slight tension, ready to contract with the 
least expenditure of force. This normal tension, or mus- 
cular tone, is due to the influence derived from the central 
nervous system ; for if we cut the nerve going to the muscle, 
it at once loses its tone, and becomes larger and relaxed. 

The muscular fibers have the power of contraction inde- 

pendent of the 
nervous system. 
This is shown by 
use of curare, 
which paralyzes the 
motor nerves, but 
does not affect the 
muscular tissue. A 
muscle thus pre- 
pared responds to 
direct stimulation. 
Similar results may 
be attained by the 
use of ammonia, 
which destroys the nerve, and yet stimulates the muscular 
tissue. 

We may study the phenomena of contraction by means 
of the muscle curve produced by a myograph (Fig. 52). The 
muscle is so arranged that its contraction moves a lever, the 
end of which comes in contact with a cylinder covered with 
smoked paper, and revolving at a fixed rate so as to receive 
a tracing of the motion of the lever. 

A muscle curve is represented in Fig. 52. From the 
study of the muscle curve produced by a single contraction we 
learn that it consists of three phases : — 

1. A latent period, during which the lever does not change 
from the horizontal line, and in which no apparent change is 




Fig. 51 —Muscle Fiber with Motoriaij 

End Plates. 
1. End plate. 2. Muscle nucleus. 3. Nerve. 



MUSCULAR ACTION. 71 

taking place. This phase is probably caused by propagation 
of the impulse along the nerve, and by the preparatory 
changes in the muscle. In the fresh muscle it occupies about 
one one-hundredth, or more correctly, probably, one four-hun- 
dredth, of a second. As the muscle becomes fatigued, this 
period becomes longer. 

2. That of contraction, causing rising of the lever. The 
height to which the lever rises becomes less as the muscle 
tires, but the duration of the phase remains the same. This 
phase occupies four one-hundredths of a second. 

3. That of relaxation, in which the muscle returns to its 
former condition, causing the descent of the lever. It occu- 




Fia. 52. — Normal Muscle Curve. 
Curve from a frog's gastrocnemius traced on a pendulum myograph. Time 
tracing of 120 double vibrations per second. Stimulus applied at a. ah (1) Latent 
period, b c (2) Contraction, c d (3) Relaxation, e (4) Slower relaxation, c. 
Height of contraction. Wavy line, time markings. (After Kutheford.) 

pies five one-hundredths of a second, but becomes longer as 
the muscle tires. 

A single muscular contraction, or twitch, is thus com- 
pleted in about one tenth of a second, but its time will vary 
with the condition of the muscle, being much longer when 
the muscle becomes fatigued. 

By sending a second shock before relaxation begins, a 
second curve is produced, and added to the first (Fig. 53) ; 
and on increasing the shock, succeeding shocks will start from 
some part of the preceding one, causing the curve to rise to 
a greater height, and end with a more sudden relaxation. 
The shocks may be increased until the interval between them 
will not be noted, the curve being a general rise. Such a 
state of continued contraction is called a tetanus. Every 
contraction of a voluntary muscle in the living body is con- 
sidered to be tetanic in nature, a sudden jerk being in reality 



72 



THE MUSCULAR SYSTEM. 



a tetanic contraction of short duration; i. e., it is produced 
by a number of quickly repeated stimuli. A fine illustration 
of a tetanus is seen in a person holding the handle of a strong 
magnetic induction machine when a current is passing. The 
hands become cramped, and the fingers bent so that one 
cannot let go of the handles. 

A fatigued or exhausted muscle cannot act, owing to the 
accumulation of the waste products from its own action. If 




Fig. 53. — Effect of Ebpeated Stimuli. 

I. Two successive shocks. II. Successive contraction produced by 12 induc- 
tions per second. III. Curve produced by very rapidrinduction shocks (complete 
tetanus). 

permitted to rest, it may recover by the circulation bringing 
fresh material and removing the waste products. 

Tetanus may be produced by some poisons, as strychnine, 
or by some disease, as lockjaw. 

The chemical changes which take place in a muscular 
contraction are very complex, and their exact nature is not 
fully known ; but we have some facts which will aid in form- 
ing an idea of their probable nature. 

The muscle cell, by its own activity, makes from the ma- 
terial furnished by the blood, or from a part of its own sub- 
stance (protoplasm), material in the form of potential 
energy, which is capable of being set free by the stimulus 
of the nerve force. This brings about a series of physical, 
chemical, and electrical changes, setting free energy that 
brings about the contraction and the resulting motion. Care- 
fully note that the cell does not die, but rather by its activity 



MUSCULAR ACTION. 73 

it effects a series of changes which produce the motion, leav- 
ing it ready to repeat over and over these changes, each time 
becoming reloaded for another change. The need of food to 
a muscle is not so much to furnish material for a new cell 
as to give it something from which it may make something, 
by the discharge of which by the nerve impulse it can pro- 
duce energy for contraction. 

We may briefly sum up the changes which take place 
during muscular contraction, viz. : — 

I. Structural. 

1. The whole muscle shortens, thickens, and hardens. 

2. The blood supply (arterial) is increased, while the 
venous blood and lymph is forced out. 

3. The sarcostyles of the fibers contract, the dark bands 
encroaching on the clear areas. 

II. Physical. 

1. There is a slight rise in temperature ; the venous blood 
from the active muscle being of a higher degree of tempera- 
ture than from a muscle at rest. 

2. A change in electric condition; a negative variation 
of the natural muscle current is produced. 

3. Increase of the extensibility of the muscle; a given 
weight stretches a contracted muscle more than it would the 
same muscle at rest. 

III. Chemical. 

1. The chemical changes taking place in a muscle are 
increased during its contraction. 

2. There is a sudden increase in the amount of carbon 
dioxide (C0 2 ), and the amount of oxygen (O) absorbed is 
increased, but not in proportion to the amount of C0 2 given 
off. 

3. Sarcolactic acid (C 3 H 6 3 )is produced, and the muscle 
becomes acid in its reaction. 

4. Kreatin(C 4 H 9 N 3 2 )is formed by the muscle at rest, 
but not by the contracting muscle. There is probably no 
nitrogenous waste during contraction. 

5. The formation of sugar ( C 6 H 1 2 O c ) , probably from the 
change which takes place in the glycogen (CgHj 5 ). 

Chemical Composition of Muscles. — As we have seen, 
there is a marked difference in the composition of the muscle 



74 THE MUSCULAR SYSTEM. 

at rest and during contraction. Even when at rest, the muscle 
is engaged in active chemical change ; carbon dioxide is given 
off, and kreatin and other products are found. While it is 
difficult to determine the exact composition of living muscle, 
yet we get many valuable facts from the study of the dead 
muscle (rigor mortis). It presents the following contrasts : — 

1. Living muscle is quite translucent; dead muscle, 
opaque. 

2. Living muscle is very elastic ; dead muscle, less elastic. 

3. Living muscle is irritable ; dead muscle gives no re- 
sponse to stimulus. 

4. Living muscle contains myosinogen and a ferment; 
dead muscle, myosin, which seems to be coagulated myo- 
sinogen. 

5. Living muscle at rest is alkaline ; dead muscle, acid at 
first, but alkaline when putrefaction sets in. 

6. Living muscle contains muscle-plasm; dead muscle, 
muscle clot (myosin) and muscle serum. 1 

Muscular Sense. — There seems to exist in the muscles a 
sense by which we are enabled to judge of the activity and 
degree of contraction of the muscles. By an examination of 
our experiences in various movements of the body we learn 
that we are conscious of the position of any part of the body, 
even with the eyes closed, and during the movement of the 
limbs we estimate the character and force of the muscular 
movement. But it is difficult for us to analyze our experi- 
ences, and to say which are due to muscle and which to the 
other sense, as they are all intimately related ; and muscular 
sensations are closely connected with cutaneous and other 
sensations, and to such a degree that some scientists doubt 
the existence of the muscular sense, independently of the 
skin. But this belief is not well founded, as cutaneous sen- 
sation may be lost or greatly impaired, while the power of 

i In addition to the products mentioned above, there are pepsin, fibrin fer- 
ments, starch (amylolytic) ferments, muscle pigment (myohematin), sarcolactic 
acid, acetic and formic acid, carbohydrates, glycogen, glucose (or maltose) 
and lnosite. 

The principal nitrogenous crystalline bodies are xanthin, hypoxanthin, 
carnin, taurin, urea, and in normal condition a very small amount of uric acid. 
The chief salt of the muscle is potassium phosphate. 



MUSCULAR SENSE. 75 

co-ordination remains ; and in the disease of the spinal cord 
called locomotor ataxia, in which the power to use the 
muscles with the proper degree of force is lost, the tactile 
temperature and pain sensation may be unimpaired. From 
the microscopic study of the muscle we learn that the muscle 
is not only supplied with fibers ending in the motorial end- 
plates, but also with different fibers, some of which are de- 
scribed as ending in fine fibrils among the muscular fibers ; 
and they probably serve for the afferent impulses of the mus- 
cular sense. The sense of fatigue is probably produced by a 
condition of the muscles. In addition to the impression 
received from the muscle itself, it is thought by some that 
tendons and ligaments may supply impulses which enter into 
the muscular sense and thought to be given by the peculiar 
nerve endings found in tendons, called the organ of GolgL 
The muscular sense is very important, and, in connection 
with the other senses, contributes much to our knowledge of 
the external world. While muscle fibers are difficult to local- 
ize, they are delicate, and enable us to arrange and force 
muscular contraction. This sense not only aids us in the 
acquiring of knowledge, but it makes possible the almost 
magic touch of the artist and other skillful manipulations. 
It is an important factor in our learning of space relations 
between things generally: but as to how the muscles help in 
these processes, whether by their own sensation or by awaken- 
ing sensations of motion in the skin, retina, and articular 
surfaces, has not been determined. It is in combination 
with these that other senses bear their most important part. 
In all the senses the muscles are more or less connected. In 
taste, the movement of the tongue is important ; in smell, the 
air carries the particles into the nose ; in hearing, the muscles 
of the tympanum contract (or those of the head) to more 
indirect sound. But it is in sight and touch that the muscles 
become of greatest importance. The most mobile parts of 
the body have the sense of touch best developed. By com- 
bination of muscular and tactile sensation, we are enabled to 
estimate small differences of weight and resistance, and thus 



7tf THE MUSCULAR SYSTEM. 

appreciate surface; and this sense, with vision, enables us 
to form an idea of perspective, or solidity and form. 

Kinds of Physical Exercise. — The value of any physical 
exercise depends much upon its nature, the number and kinds 
of muscles it calls into action, and the effect it has upon the 
body in general. 

According to the quantity of work represented by an exer- 
cise, it is said to be gentle, moderate, or violent. When the 
quantity demanded is small, as in walking slowly, the exercise 
is called gentle; when more work is done, as in walking 
briskly, it is called moderate ; when large in quantity, as in 
running, it is said to be violent. 

But quantity alone cannot be taken as a standard by which 
to measure the value of an exercise ; for although the quan- 
tity of work done in two cases may be the same, yet the effect 
of the exercise on the system may be quite different, from 
the number and relation of the muscles brought into action, 
and the different conditions under which it places the other 
organs of the body. 

There should be a clear distinction made between diffi- 
culty of work and quantity of work; if not, we shall make 
serious mistakes in choosing exercises for health. Many of 
the so-called violent exercises and exercises of strength are 
only exercises of skill, and in many difficult exercises we 
really do the same amount of work that we do in others which 
seem to be easy ; e. g., a little girl will skip one hundred times 
in a minute, jumping six inches high, but how much more 
difficult for her to raise herself fifty feet high in one minute 
by means of rings placed six inches apart ; and yet the work 
done in each case is the same. What makes the latter more 
difficult is that the body has to be raised by the smaller and 
weaker muscles of the arms, while in skipping, the work is 
done by the strong muscles of the lower limbs. 

Exercises of Strength Exercises of strength are those 

in which each movement represents a great quantity of work, 
and calls into action the contractile power of a great number 
of muscles, as carrying a heavy burden. 



EFFECTS OF EXERCISE. 77 

In exercises of strength, will, as well as muscle, is neces- 
sary. Other things heing equal, the man with stronger will 
produces the more muscular energy, as his muscles will con- 
tract more vigorously under the stimulus of a strong will. In 
exercises of great strength, the whole body is put into a state 
of rigidity, that the various parts may act either for support 
or leverage, the breath is held, and the veins of the thorax 
are compressed; the elimination of carbon dioxide is thus 
hindered at the time when it is being most rapidly generated. 
They further lead to the compression of the great arteries, 
the veins, and the heart, producing a profound disturbance in 
the pulmonary circulation just at the time when pure blood 
is most needed, so that in protracted efforts the person has to 
stop for breath before the muscles are fatigued. It will be 
seen that such exercise is not the kind suitable to a stu- 
dent or the person of sedentary habits, whose circulation is 
already sluggish, and whose nerves are more or less exhausted. 
An exercise which makes a drain of will power is not suited 
to those who are mentally fatigued. 

Exercises of strength demand greater muscular expendi- 
ture, but they produce all the conditions necessary for ener- 
getic tissue repair. They demand very little co-ordination, 
and do not demand frequent repetition of movement. They 
make a less disturbance of the nerves than exercise of speed, 
and do not make the drain on the brain, like exercise of skill. 
This form of exercise is favorable to all nutritive functions, 
increasing the activity of all the organs of the body, while 
leaving in relative repose the nerve centers and psychical 
faculties. Such exercises tend to increase the weight of the 
body. 

Exercises of Speed. — Exercises of speed are those in 
which there is very frequent repetition of muscular move- 
ment. The various exercises of speed differ very much as 
regards the intensity of work. Running is a violent exer- 
cise, while in piano playing, although the fingers are moved 
with extreme speed, there is a very slight expenditure of 
energy. 



78 THE MUSCULAR SYSTEM. 

In considering exercise of speed, two things are to be 
noticed : 1, the rapidity with which work accumulates ; 2, the 
speed with which movements succeed each other. 

The rapidity with which work accumulates depends upon 
(1) the quantity of work represented by each muscular effort, 
and (2) the number of these efforts in a given unit of time. 
A person going slowly upstairs with a heavy burden, and a 
person running as fast as he can along a level road, are both 
doing a great quantity of work in a short time ; one by very 
slow movement, the other by very rapid movements. In 
each case work accumulates. The formation of carbon dioxide 
is in proportion to the sum total of energy expended in a 
given time. The thirst for air is closely related to the carbon 
dioxide produced. This thirst for air is produced by intense 
muscular work, be it from speed or strength. In running 
at simple play, one absorbs, without making any painful 
muscular effort, a greater quantity of oxygen than one 
who has been made to use heavy dumb-bells, although the 
amount of work done may be the same. In exercises of 
speed, the greater exhaustion is of the nervous energy. It 
has a marked effect on nutrition, as shown by men accustomed 
to exercises of strength; as porters, who are usually of a 
massive build, become more so as they practice their occupa- 
tion, while those engaged in exercises of speed, as runners 
and fencers, are generally of slender build. 

Exercises of Endurance. — In exercises of endurance the 
work is continued for a long time. The expenditure of 
force is determined less by the intensity and rapidity of suc- 
cessive efforts than by their duration. 

In an exercise of strength, work accumulates, as each mus- 
cular effort is very intense. In an exercise of speed, work 
multiplies ; for while the movements have little energy, they 
come in such rapid succession that the small intensity leads 
in the end to accumulation of work. In exercise of endur- 
ance, the muscular efforts following the period of rest after 
sufficient interval, the work is fractional, the quantity of 
work not exceeding its power of resistance. An exercise of 
endurance may become an exercise of speed, if the efforts 



EFFECTS OF EXERCISE. 79 

follow in rapid succession ; or one of strength, if the effort is 
greater than the power of resistance; i. e., is beyond the 
strength of the individual. 

To the man learning it, rowing seems to be an exercise of 
strength ; for the waterman, it is only one of endurance, he 
being able to row all day without unusual fatigue. The great 
difference we notice in persons as respects their power to 
endure continued work, is due largely to their different res- 
piratory powers. 

In order that an exercise may be long continued, it must 
not lead to breathlessness. " We can go on walking in spite 
of weary limbs and sore feet, but we cannot go on running 
when we are out of breath." 

The physiological effect of exercise of endurance is to 
spare the organs, while increasing, in a salutary degree, the 
play of their functions. One of its most marked features is 
that it gives the organ power of repairing, even while doing 
the work. Thus the carbon dioxide is removed from the sys- 
tem as fast as formed, and there is also a considerable increase 
in the amount of oxygen. 

While exercises of endurance have the advantages men- 
tioned, there is one very important disadvantage ; i. e., while 
they render more active the interchange of gases, and enrich 
the blood with a greater quantity of oxygen, they do not call 
into action the entire capacity of the lung, thus causing every 
air cell to become inflated and active, and bringing about a 
healthier action and a fuller development of the lungs. 

Exercises of endurance (1) allow the performance of 
work with great economy of fatigue; (2) they give the sys- 
tem the benefit of a supplementary acquisition of oxygen 
without exposing it to the dangers of forced respiration. 

Time for Exercise. — The time for exercise is important, 
and must be largely determined by the habits and condition 
of the individual. If the person is strong, exercise on rising 
in the morning, and before breakfast, may be engaged in with 
good results to the person; but persons enfeebled by poor 
health or age should not engage in such exercises, or if at 
all, only in very gentle exercise. 



80 THE MUSCULAR SYSTEM. 

It is a very safe rule never to engage in vigorous exercise 
just before or after a meal. As we have seen, a large blood 
supply is needed for vigorous exercise. If this demand is 
made during the time of the digestion of a meal, the organs 
are deprived of their proper food supply, and thus interfere 
with the process of digestion. 

We should not engage in vigorous exercise when fatigued 
from mental or nervous strain, as nerve force is needed in 
muscular effort as well as in mental activity. If the exercise 
is moderate, however, it may be of benefit. 

The Place of Exercise. — If possible this should be in the 
open air and in the sunshine. If this cannot be done, the 
room in which the exercise is taken should be well ventilated 
and well lighted. 

The Amount of Exercise. — The amount and kind of exer- 
cise must be governed by the age and physical condition of 
the person. Very vigorous persons may engage in exercises 
of strength ; the young, in those of speed ; the feeble and aged, 
in those of endurance, the intensity varying according to the 
strength of the individual. The young should not be called 
upon to do heavy tasks, as they have upon them the extra 
demands of growth; and if the exercise is carried to 
extremes, it will interfere with their development. The 
exercise should never be carried to the point of extreme 
fatigue. If our resting fails to rest us, or restore our vigor, 
or if it fails to give us strength, it should be a warning to us 
that we are overworking ourselves ; we should at once lessen 
the amount or degree of the exercise. 

Regularity of the Exercise. — It is very important that 
the amount and time of the exercise should be regular. 
Strength is not gained by spasmodic efforts. It is the regular, 
persistent exercise that gives strength and tone to the muscles 
and vigor to the body. 

Variety of Exercise. — The exercise should be varied, so 
as to call into action as many muscles as possible. Probably 
there is no one exercise that will do this, so we should vary 
our exercises. A careful study of the muscles called into 



EFFECTS OF ALCOHOL. 81 

action by the various exercises will enable us to choose those 
best adapted to our purpose. We should consult some good 
work on physical training whose province it is to discuss this 
question, rather than that of an elementary physiology. 

Manner. — The exercise should not be violent, such as 
would lead to a quick exhaustion. The change from rest to 
motion, and the change from motion to rest, should be 
gradual. When too sudden, it brings too great a strain upon 
the vital organs, especially the heart, which, it must be 
remembered, is a very delicate organ. 

Effects of Alcohol on the Muscles. — We can trace the 
effects of alcohol on an organ to one or all of three sources : 
(1) the nerves, (2) the blood vessels, (3) metabolism of the 
cells. As we have seen, the muscles are classed with the 
master tissues of the body, and injury to them therefore 
means serious injury to the entire organism. 

The injury to the muscles through the nerves by the 
habitual use of alcoholic drink is shown as follows : — 

1. Loss of muscular control, as seen in the person when 
intoxicated. While this is temporary, its constant repetition 
will result in serious injury to the muscular control and co- 
ordination. Such muscles will lack power and accuracy in 
their contraction, thus destroying the skill and power of 
the person possessing them. 

2. Through the overstimulation they are forced to over- 
work, and thus are exhausted, which is especially true of the 
heart. 

3. By the stimulation of the vaso-dilator nerves by the 
dilation of the blood vessels, which brings to the muscles an 
undue blood supply. While blood is needed, too large a pro- 
portion is injurious. 

4. Alcohol affects the chemical changes (metabolism) 
which take place in the cell, causing them to change the pro- 
toplasm into fat producing ("fatty degeneration"), which 
takes away from the muscle its contractibility. This fre- 
quently takes place in the muscles of the heart. 

The laborer, the mechanic, and the artist, whose best cap- 
ital is their muscular touch and skill, are robbing themselves 
when they take alcohol as a beverage, because it will take 
from them their skill, destroy their usefulness, and rob them 
of their means of support. 
6 



CHAPTER V. 

THE NERVOUS SYSTEM. 
EXPERIMENTS AND DEMONSTRATION. 

I. Dissection of the Brain. — Remove the bone from the 
upper part of the skull so as to expose the brain. This 
may be easily done by means of the bone forceps if care 
is taken not to injure the brain substance by pressure. 
Carefully cut away the investing membrane {dura mater), 
and handle the brain carefully, so as to avoid tearing the 
nerve roots. Notice at what points the more important 
branches are given off from the brain, and where they 
enter the skull. Notice that the cavity in which the brain 
is found is continuous with that of the vertebral column. 
Clip off the lower portion of the brain where it passes 
into the spinal canal. The large opening through which 
it passes is called the foramen magnum (Fig. 90). Notice 
carefully how the brain rests in the skull. In removing it, 
care should be taken not to cut the large arteries. 

It is best to wash out the blood vessels by injecting 
them with a salt solution, afterward filling them with a 
ninety-per-cent solution of strong spirits and then tying 
them. The brain should then be placed in a solution con- 
sisting of sixty parts of ninety-five-per-cent alcohol and forty 
parts of two-per-cent formalin. It is best to have four 
or five times as much of the solution by volume as there 
is of the brain. It is generally best to put it into a weak 
(fifty per cent) solution of spirits, and then remove it to 
the stronger solution, in which it should remain for a month 
or more to harden it thoroughly. 

Under the subject of circulation is given directions for 
injecting the brain. 

1. Notice (a) the large front mass (cerebrum), and 
make a careful note of its surface markings; (b) the por- 
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EXPERIMENTS. 83 

tion overlapped by the cerebrum (cerebellum), and compare 
its surface with that of the cerebrum; (c) the club-shaped 
mass in front of the cerebellum, and beneath the cerebrum 
{medulla oblongata). 

2. Turn back the cerebellum, and tear away the mem- 
brane (pia mater) which dips down in front of it. Notice 
(a) two round and rather large bodies in front of two 
small bodies, which make up the corpora quadrigemina; (b) 
going from the cerebellum on each side, and disappearing 
beneath the posterior corpus quadrigeminum of the same 
side, rounded cords, the superior peduncles of the cerebel- 
lum ; (c) a thin layer of nervous substance stretching between 
the superior peduncles, and covering the front part of the 
fourth ventricle, which can be exposed by removing this 
membrane (valve of Vieussens). In the interior part of 
the valve may be seen the roots of the fourth nerve. 

3. Examine the under, or ventral, surface of the medulla 
oblongata. Do not tear away the pia mater. (a) Ex- 
amine the two round cords on each side of the middle 
line (median) — the anterior pyramids. (b) Notice the 
transverse fibers — the pons Varolii. (c) Notice two 
slightly oval elevations, one on each side of the anterior 
pyramids, the inferior olivary bodies. They may be more 
plainly seen by tearing away the pia mater, (d) Observe 
two broad, rounded bands which appear at the anterior edge 
of the pons, passing forward, and diverging from one an- 
other — the crura cerebri, (e) Notice two flat bundles of 
fibers coming obliquely forward over the front part of the 
crura cerebri, and meeting in the median line to form the 
optic cliiasma, the separate parts of which are known as the 
optic tract. 

4. Examine carefully the surface. Notice (a) the 
depression (fissure) on the upper surface of the cerebrum, 
running backward, — the great median fissure, which sepa- 
rates the cerebrum into two parts (hemispheres) ; (b) the 
groove on the under surface, passing obliquely upward, — 
the fissure of Sylvius; (c) the fissure separating the cere- 
brum from the cerebellum, — the transverse fissure. 

5. Divide the brain in halves by a longitudinal section 
through the median fissure. Observe (a) the obliquely cut 
fibers in the decussation of the pyramids; (b) the trans- 
versely cut fibers of the lower part of the pons; (c) the cor- 



84 THE NERVOUS SYSTEM. 

pora quadrigemina ; (d) the posterior commissure; (e) 
the pineal gland; (/) the large middle commissure, which 
occupies a large portiou of the third ventricle; (g) the cor- 
pus callosum; (h) the septum lucidum, deep anteriorly 
between the corpus callosum and fornix; (%) the pia mater 
entering the transverse fissure, forming at this point the 
velum interpositum situated beneath the fornix and over the 
optic thalami; (;) the curious arrangement of the gray mat- 
ter of the cut portion of the cerebellum, resembling a tree, 
and known as the arbor vita?. 

II. Histology. — Harden a rabbit's or a cat's brain in 
a two-per-cent solution of ammonium potassium dichromate, 
putting it into a new solution the following day. The brain 
should then be cut transversely, put into a fresh solution 
for a week; and then removed to a fresh solution, in 
which it can be left two or three weeks. It should then 
be cut into pieces, care being taken to note what portion 
the pieces are from, and washed in a dilute solution of alco- 
hol (thirty to fifty per cent) to remove the excess of 
chromate salt. Stain the pieces by keeping them in strong 
Prey's carmine for a week or more; wash well in water, 
soak in gum, cut with a freezing microtome, clear, and 
mount in Canada balsam. 

Try to find the following : — 

1. The inner layer of horizontal nerve fibers which 
form the white substance. Notice how the fibers enter the 
outer gray substance (cortex). The irregular-shaped cells 
found between the fibers are called leucocytes. 

2. The layer of small nerve cells at the outside fibrous 
layer, and forming the fifth layer of the gray substance of 
the cortex. 

3. A layer of small cells of various shapes, with three 
or more well-marked processes situated beyond the last layer, 
and forming the fourth layer of the cortex. 

4. Following the last layer, one made of pyramidal 
cells, giving off from their apexes a process which continues 
upward for some distance. This forms the third layer of 
the cortex. Note its relative thickness, and the change in 
the size of the cell. 

5. The next layer, of numerous small pyramid cells 



EXPERIMENTS. 85 

with well-marked process pointing outward. Tins layer 
forms the second layer of pyramidal cells of the cortex. 

6. The outer layer, made lip of a fine network of fibrils, 
in which will be found a few very small cells. 

7. See if you can find traces of any blood vessels in 
the cortex. Where are they most numerous ? From what 
are they derived ? 

III. Microscopic Structure of the Cerebellum. — Take a 
portion of the cerebellum, prepared as in the last experi- 
ment, making section from the surface of the inner white 
substance, and at right angles to the direction of the folds. 
Mount as directed for the cerebral cortex. Notice, — 

1. The inner strand of medullated fibers. 

2. A layer of cells, formed principally of small cells 
closely packed together, forming the nuclear layer. The 
cells have but a small amount of cell substance, so that when 
deeply stained we only see their nuclei. 

3. A single layer of large, somewhat globular cells 
(Purkinje's cells), with large processes which often branch. 
See if you can trace any of them to the surface of the 
cortex. 

4. The outer layer, consisting of scattered, small, an- 
gular cells, with relatively large nuclei, and often giving 
off one or more branching processes, all intermingled with 
the fibers from the cells of Purkinje, and imbedded in a 
close fibrillar network. Notice the numerous capillaries in 
this layer. 

IV. The Cranial Nerves. — 1. Notice the club-shaped 
bodies extending forward from the fore part of the cerebral 
hemispheres — the olfactory lobes. Trace this and the other 
pairs as far as you can, to find to wdiat they go, and their 
functions. 

2. Trace the nerves which come from the eyes (the 
optic nerves) to where they join, then cross to pass to their 
origin in the anterior corpora quadrigemina. 

3. Back of the optic nerve, near the median line, are 
two nerves, the third or motor oculi nerves, which have their 
origin in the crura cerebri. 

4. On each side of the groove between the cerebrum 
and the cerebellum there will be seen the origin of the fourth 
pair, or trochlear nerves. 



86 THE NERVOUS SYSTEM. 

5. Just back of the fourth pair notice a pair of nerves 
which originate by two roots; a large sensory root, con- 
nected with a knot, or ganglion (the Gasserian ganglion), 
and a smaller root, which has no ganglion. These are 
known as the fifth pair, or trigeminal nerves. They have 
their deep origin in the floor of the fourth ventricle. 

6. Back and inside of the fifth, pair, and arising from 
the front part of the floor of the fourth ventricle, is the 
sixth pair, or abducens nerves. 

I. Emerging from the medulla, between the restiform 
and olivary bodies, is a pair of large nerves, the seventh, 
or facial nerves. Their deep origin is near that of the sixth, 
in the fourth ventricle. 

8. Back of the seventh pair are the nerves which are 
distributed to the ear, the eighth pair, or auditory nerves. 
Their deep origin is very complicated, but part of the fibers 
have their origin in the fourth ventricle. 

9. The ninth, tenth, and eleventh pairs arise close to- 
gether, farther back, and well upon the sides of the medulla. 
The nucleus of the ninth pair, or glossopharyngeal nerves, 
is in the floor of the lower part of the fourth ventricle. 

10. Observe the nerves originating by eight or ten fil- 
aments from the groove between the restiform and olivary 
bodies below the glosso-pharyngeal ; this pair is the tenth, 
or pneumo gastric nerves. They have their deep origin in the 
lower part of the fourth ventricle, below the area of the ninth. 
Trace out, and determine its distribution. How does its dis- 
tribution compare with that of the other cranial nerves ? 

II. The eleventh pair has two parts, the spinal acces- 
sory proper, formed by the roots from the cervical spinal 
cord, and the bulhular accessory, whose roots come off just 
below the pneumogastric. The deep origin of the bulbular 
accessory is common to it and the vagus. 

12. Notice the nucleus near the middle of the floor of 
the lower part of the twelfth pair, or the hypo-glossal nerves. 

V. Dissection of the Spinal Cord.' — Carefully cut away 
the bone from the posterior part of the spinal cord by use of 
the bone forceps, to break away the bone, being careful not 
to injure the cord. 

1. Observe the numerous threads of nerves {spinal 
nerves) given off on each side. Discover if you can how 



THE SPINAL CORD. 87 

they get out of the bony canal in which they are placed. 
J )o the libers which go from the back part {posterior) differ 
from those which go from the front (anterior) ? The little 
knots found on the posterior pair are called ganglia. Can 
you suggest a name for them? (If the specimen has been 
injected, carefully note the relation of the blood vessels.) 
How many pairs do you find ? Does the spinal cord con- 
tinue the entire length of the bony canal (spinal canal) in 
which it is found ? To determine this you will have to cut 
the covering of the cord from above downward. 

2. Xote the number and relation of the enlargements 
of the cord. Can you discover any reason for these enlarge- 
ments ? 

3. Can you account for the bunch of fibers at the end 
of the upper limbs ? of the lower limbs ? Do they come 
from the brain or the spinal cord ? 

Harden a spinal cord in potassium dichromate as directed 
for the brain. If you cut the spinal cord into transverse 
pieces, be very careful to mark them so you can tell their 
relation. Hake a transverse section just above the origin 
of the first nerve of the neck (cervical nerves). 

Observe, — 

1. Covering of the cord. 

2. The depression on the anterior side (anterior fis- 
sure). Examine with two-thirds- or three-fourths-inch objec- 
tive and C eye-pieces. 

3. The depression on the posterior side (posterior fis- 
sure). How do these fissures compare in depth and width? 

4. The darker, irregular central mass, the gray matter, 
and around this the white matter. The projecting portions 
are called cornua. Xotice the portions which project back- 
ward (posterior cornua), and those which project forward 
(anterior cornua). How do these cornua differ? 

5. The hole near the center of the cord (the central 
canal). Is it lined with cells? (Examine with one-sixth- 
inch objective). 

6. Make a careful examination under high power of the 
gray matter and the white matter. 

7. Examine sections from the different regions of the 
cord, carefully noting the relative proportion of the white 
and gray matter, and the position and size of the central 
canal in the different regions. 



88 THE NERVOUS SYSTEM. 

8. Make longitudinal and transverse sections of the 
posterior ganglion. Make several sections. If the nerve 
cells of the ganglion are pear-shaped, how can you account 
for the difference in size of cells in the section you examined ? 

9. Also make sections of the nerves, and examine them 
under a lens of high power. 

VI. The Sympathetic Chain. — 1. Having traced the 
pneumogastric to the neck, you will find it bound in the 
same sheath with the sympathetic nerve. Trace it until 
you come to the ganglion of the pneumogastric, near which 
will be found an enlargement of the sympathetic nerve, the 
superior cervical ganglion. Carefully dissect out the rest 
of the chain. Determine if you can if there is any con- 
nection between the spinal nerves and those of the sympa- 
thetic. At what points do you find the most nerves given 
off ? See if any of these can be traced to network of nerves 
and ganglia (plexuses). How many pairs of ganglia do 
you find ? How does the sympathetic chain terminate below ? 

2. Carefully tease out some of the nerve fibers as 
directed in the experiment given below. 

VII. Histology of Nerve Tissue. — 1. The structure of a 
nerve. 

a. Remove the skin from the back of the thigh; cut 
through the tendonous line seen over the femur, and pull 
the outside mass of muscle outward, which will bring to 
view a large glistening thread (the sciatic nerve). 

b. Remove a small portion of the nerve, tease it out very 
carefully in a one-half-per-cent salt solution, and mount as 
directed for teased specimens. 

Notice, — 

( 1 ) The nerve is made up of smaller threads or fibers. 

(2) The transparent sheath on its surface appears hya- 
line, but when seen on edge presents a double outline; this 
sheath is the medullary sheath. Observe the change in the 
appearance in the nerve which takes place on standing. 

(3) Take a bundle of nerve fibers from the optic nerve, 
macerate for twenty-four hours in iodized serum, and then 
prepare by teasing. The gray central line is the axis cylinder. 

(4) Harden a nerve in alcohol or dilute chromic acid, 



THE SPINAL CORD. 89 

and stain some of the sections in picrocarmine and others 
in hematoxylin. Make transverse sections, and mount in 
dammar or balsam. Note, — (a) the well-defined connective 
tissue sheath-covering (neurilemma), covering the nerve 
fibers, and varying in size with the fibers which it invests ; (b) 
the rings presenting double contour — the medullary sheath. 
2. The Nerve Cells. — Examine and make drawings of — 

( 1 ) Various sections of a posterior ganglion. 

(2) Various cells of sympathetic ganglia. 

(3) Sections of the spinal cord in the cervical, dorsal, 
and lumbar regions. 

In each case note carefully the shape of the cells, and 
their relations. 

VIII. Nerve Action. — 1. Tickle the inside of the nose 
with a feather. Account for the action produced. 

2. Feign to strike the eye with the finger. Account for 
the action. 

3. Kill a frog with chloroform. Eemove the brain, leav- 
ing the cord intact. 

(1) Pinch the toe, and note action produced. 

(2) Dip small bits of sponge in a dilute acid (strong vin- 
egar will do), place them on different parts of the body, and 
notice the difference in action produced. After each appli- 
cation, thoroughly wash the parts with water. 

(3) Put a drop of acid on the flank of the frog. Note 
the action. Hold the foot on the side to which you added 
the acid. Explain the action. 

(4) Expose the sciatic nerve near its origin. Pinch the 
terminal parts, and notice results. 

THE NERVOUS SYSTEM TEXT. 

Need. — Motion is essential to our existence and best 
development. Not only must the organs act, but they must 
act in harmony, both as to degree and kind of motion. These 
movements must not be made in reference to the body alone, 
but also to the environment of the body, to which it must 
adapt itself. But this power of motion, — sense of relation- 
ship, — not only of its own parts, but of the environment 
controlling and directing, cannot originate within the bones 
and muscles. It must come from without these organs. 
The system of organs by which this is accomplished is 



90 THE NERVOUS SYSTEM. 

called the nervous system. The more highly developed 
this system, the higher and richer the physical and intellec- 
tual life of the organism. Hence man stands pre-eminent 
among created forms, the masterpiece of the Archi- 
tect of the nniverse. Should we not prize our high 
estate ? The impressions (sensations) from without are 
signs of the change of our environment; the impulses to 
the organs causing them to act so as to bring our body in 
harmony with our environment are called stimuli. The 
condition of the parts of the body, and the harmonious 
action to adapt these parts to secure the best development, is 
brought about in the same way — by sensations and stimuli. 

Divisions. — The nervous system, for convenience of study, 
may be grouped into two divisions, the Central Nervous, 
or Cerebrospinal System, and the Sympathetic, or Gan- 
glionic System. We have learned from our dissections 
that the central nervous system is found in the neural 
cavity, and that it sends off branches (nerves) to various 
parts of the body. It consists of the brain, spinal cord, 
and cranial and spinal nerves. The sympathetic is located 
in the ventral cavity, and consists of a double chain of 
nerve masses (ganglia), numerous scattered ganglia, plex- 
uses, and sympathetic nerves. 

The last is not a distinct system, as was once thought, 
but only an outlaying part of the same system, and in close 
connection (Fig. 57) with it, most of its fibers being derived 
from the central nervous system. 

As we have seen, nerves go to nearly every organ and 
tissue of the body. That these various parts may work in 
harmony, it is essential that the entire system be under the 
control of a central guiding force. This we find in the brain. 

While the brain is the central and controlling organ, on 
account of its simple structure, it is better to consider first 
the spinal cord. 

THE SPINAL CORD. 

General View of the Cord. — The cylindrical mass of 
nervous matter contained in the spinal canal is called the 



THE SPINAL CORD. 



91 



spinal cord. It extends from 
the margin of the foramen 
magnum of the occipital bone 
to the first lumbar vertebra, 
where it ends in a slender 
thread, the filum terminal e, 
which lies among a mass of 
nerve roots called the cauda 
equina (Fig. 5-1). It is from 
seventeen to eighteen inches 
long and three fourths of an 
inch in diameter in a person 
of average height. 

The spinal cord gives off 
thirty-one pairs of nerves, 
which leave the spinal canal 
by openings called the inter- 
vertebral foramen. 

The spinal cord is not of 
uniform size, but presents 
two enlargements: (1) the 
lumbar swelling, beginning 
at the first lumbar and ex- 
tending to the eighth dorsal, 
and being widest near the 
third lumbar. From the 
lumbar swelling, the cord re- 
tains very nearly the same 
diameter until it reaches the 
level of the seventh cervical, 
when it has a (2) fusiform 
enlargement, which extends 
to the bulb, being broadest 
at the level of the fifth or 
sixth cervical nerve. The 
sectional area of the cord in- 
creases from below upward, 



,/\V; 



J-fl 



? 



A. B. 

Fig. 54. A.— With Coverings Partly 

Removed. 
1. Second cervical nerve. 2. Ligament- 
um dentata. 3. First dorsal nerve. 4. 
First lumbar. 5. Cauda equina. 6. First 
sacral. 

Fig. 54. B. — General, View of the 
Spinal Cord Without Coverings. 
1. Funiculus gracilis. 2. Funiculus 
cuneatus. 3. Posterior intermediate fis- 
sure. 4. Cervical enlargement. 5. Pos- 
terior median fissure. 6. Posterior lateral 
fissure. 7. Posterior column. 8. Lateral 
cohimn. 9. Lumbar enlargement. 10. 
Terminal cone. 11. Beginning of filum 
terminale. 



92 THE NERVOUS SYSTEM. 

but not regularly, the irregularity being due to the lumbar 
swelling (Fig. 54). The spinal cord does not completely fill 
the spinal canal. It is invested by three membranes, with a 
space between the outer and middle ones, and another space 
between the middle and inner ones. 

Membrane of the Cord. — The outer membrane is the dura 
mater, and is continuous with that of the brain, but differing 
from that of the brain, in that it is not connected to the bony 
walls, but separated from them by areolar tissue and a plexus 
of veins. It sends oif tubular sheaths along the spinal nerves 
for a short distance, and becomes lost with their investing 
membranes as they leave the intervertebral foramen. 

Beneath the dura mater is found a thin, delicate mem- 
brane, the arachnoid membrane. It is also continuous with 
the cerebral arachnoid above. It also passes as a sheath 
for the nerves, and is separated from the dura mater by a 
narrow space termed the subdural space. 

Beneath the arachnoid is a vascular membrane {pia 
mater) closely attached to the surface of the cord, dipping 
down into its fissures, and sending investments along the 
nerves. The pia mater is loosely connected with the arach- 
noid by strands of connective tissue, forming a spongy 
network, but there is a considerable space between 
the two, which is called the subarachnoid space. This 
space contains a fluid called the cerebrospinal fluid. This 
may be considered as a serous, or lymphatic, space, and is 
in communication with the perivascular lymphatics of the 
small arteries that pass into the nervous tissue of the 
brain, and spinal cord from the pia mater, as well as with 
lymph spaces in the nervous matter itself. It is also in 
communication with the central canal of the cord and the 
ventricles of the brain, by a small opening through the pia 
mater in the roof of the fourth ventricle. This opening 
is called the foramen of Magendie (Fig. 64). 

This fluid differs from ordinary lymph, (1) in its small 
per cent of proteids; (2) in the absence of cells; (3) in 
the absence of a fibrin ferment. It finds its way back into 



THE SPINAL CORD. 



93 



the circulation by escaping into the lymphatics of the nerves 
in the subarachnoid space around their roots, and from them 
into the general lymphatics of the body. 

The pia mater is attached along its whole length on 
each side, between the anterior and posterior roots of the 
spinal nerves, to a narrow fibrous band of connective tissue, 

e . which is 

joined at in- 
tervals by 
tooth-like pro- 
jections to the 
dura mater. 
The band is 
called the liga- 
mentum den- 
ticulatum. 

We can best 
get a view of 
the general 
structure o f 
the cord by an 
examina- 
tion of trans- 
verse sections 

of various 
■Transverse Section of Spinal Oord in _ a„ Yrru,"i~ 

CERVICAL REGION. P &rtS - gillie 

1. Posterior root. 2. Reticular formation. 3. Anterior the Se differ 
root. 4. Anterior fissure. 5. Central canal. 6. Posterior 

fissure. . somewhat, 

they have many features in common. Fig. 55 illustrates 
the general structure. There are two fissures running along 
the length of the cord, which divide it into a right and a 
left half. This fissure, called the median fissure (Fig. 55), 
is divided into two parts ; one in front, the anterior median 
fissure (Fig. 55), which is the wider but shallower of the 
two, and is closely invested by the pia mater, and one in 
the rear, the posterior median fissure (Fig. 55). The pos- 
terior fissure is not a true fissure, but more of a septum of 




Fig. 55. A. 



94 



THE NERVOUS SYSTEM. 



connective tissue and blood vessels passing nearly to the 
center of the cord. There are also fissures or furrows on the 
side of the cord, known as lateral fissures. The one at the 
line of attachment of the posterior roots of the spinal nerves 
is called the posterior lateral groove (Fig. 54) ; the one at 
the attachment of the anterior roots, though not marked by 

any furrow, and 
spread over some 
space, may be re- 
garded as indicating 
another division of 
the cord. In the up- 
per part of the cord 
there is a slight 
longitudinal furrow 
(Fig. 54), the pos- 
terior lateral furrow. 
It is not far from 
the posterior median 
fissure. Each half 
of the cord is thus 
divided into four 
columns: the portion 
between the anterior 
median fissure and 
the anterior roots, the 
anterior column; be- 
tween the line of or- 
igin of the anterior roots and posterior roots, the lateral 
column; between the line of origin of the posterior roots 
and the posterior lateral furrow, the posterior median col- 
umn; between the posterior lateral and posterior median 
fissure, the posterior column. 

The transverse sections also show us that the cord con- 
sists of gray and white matter: the white matter is on the 
outside, and gives to the cord its white opaque appearance; 
the gray matter is on the interior, and is arranged in the 




Fig. 55. B— Transverse Section of Spinal 
Cord in Dorsal Region. 

1. Posterior root. 2. Reticular formation. 3. 
Anterior root. 4. Anterior fissure. 5. Central 
canal. 6. Posterior fissure. 



THE SPINAL CORD. 



95 



form of a crescent or comma-shaped mass in each half, 
being joined in the middle by a mass of gray matter, the 
gray commissure. In the center of the gray commissure 
is tie central canal, the cord, which is lined in early life by 
ciliated columnar epithelium. At the bottom of the an- 
terior fissure is a. transverse connecting portion of white sub- 
stance, the anterior, or 
white commissure. x\t 
the outer side of each 
crescent the gray matter 
forms a kind of network 
(processus reticularis). 
The horns of the cres- 
cent are named from 
their position, the an- 
terior and posterior. As 
we have seen, the 
amount and form of the 
gjrav matter varies in 
different parts of the 
cord. 

In the cervical region 
(Fig. 55) the anterior 
cornu is large and broad 
and the posterior cornu 
narrow; in the dorsal 
(Fig. 55) and thoracic 
regions both anterior 
and posterior cornu are narrow; in the lumbar region (Fig. 
55) the anterior and posterior cornu are broad. The relative 
proportion of white and gray matter varies in the different 
regions of the cord (Fig. 55), being least in the thoracic and 
dorsal regions and greatest in the lumbar region. The sections 
of white matter increase in absolute size, in a steady manner, 
on the whole, from below upward. The gray matter varies 
greatly in absolute area. At the level of the third lumbar 
region the gray matter is much reduced. At the level of the 




Fig. 55. C— Transverse Section of Spinal 
Cord in Lumbar Region. 
1. Posterior root. 2. Anterior root. 3. Cen- 
tral canal. 



96 THE NERVOUS SYSTEM. 

sixth cervical region it again increases to a considerable 
amount. 

Microscopic Structure of the Cord. — The white matter of 
the cord is composed of medullated nerve fibers, but these do 
not have the sheath of Schwann, which runs for the most 
part in a longitudinal direction, so that they appear in 
cross section as minute circles. Their size varies in differ- 
ent parts of the cord, those near the surface being larger 
than those near the gray matter. The supporting tissue of 
the fibers is a peculiar fibro-cellular structure, the neuroglia, 
and in part connective tissue. The neuroglia is abundant 
at the surface of the cord, and extends into the gray matter 
forming the gelatinous substance (substantia gelatinosa) 
upon which rests the epithelium of the central canal ; it also 
tips the posterior cornu. 

The gray matter is made up of nerve cells with branch- 
ing processes, fine medullated fibers and neuroglia, and non- 
medullated fibers. The nervous filaments run in various 
directions, and while they do not form a plexus proper, by 
anastomosing they make an interlacement of extreme com- 
plexity. 

The cells of the gray matter are more or less regularly 
arranged in areas or columns. The cells of the anterior 
cornu are called the vesicular column of cells (Fig. 55). 
They are large multipolar cells, each of which has an axis- 
cylinder process, continuous with a fiber of the anterior 
root of a spinal nerve, the other process breaking up into 
a fine meshwork of fibrils. These cells are most numerous 
in the cervical and lumbar enlargements. The cells of the 
posterior horn are much smaller, and any axis-cylinder 
they may possess does not seem to be connected with 
posterior fibers, but pass to the anterior horn. A group 
or tract of medium-size cells, situated at the inner angle 
of the base of the posterior horn, is called Clarice's column 
(Fig. 56). There is also another group in the lateral cornu 
of gray matter. 



THE SPINAL CORD. 
A * 



97 




\ .e 




Fig. 56. — Motor and Sensory Tracts of the Spinal Cord. 

A. Section of cervical region, a. Posterior column. 1. Column of Goll. 
2. Comma tract (Schultz's comma). 3. Column of Burdach. 

b. Lateral column. 5. Direct cerebellar tract. 6. Crossed pyramidal tract. 
8. Antero-lateral ascending tract (tract of Gowers). c. Anterior column. 
10. Direct pyramidal tract. 

B. Section in dorsal region. Parts numbered as in A. 
0. Section in lumbar region. Parts numbered as In A. 

7 



98 THE NERVOUS SYSTEM. 

COLUMNS OF WHITE MATTER. 

We have seen that by the superficial fissure the white 
matter of the cord is divided into columns ; these, on closer 
examination, are found to be made up of other tracts. 

The principal means by which we determine this are: 
(1) By cutting the fibers loose from the nerve cell (the Wal- 
lerian method). If the fiber is separated from its cell, it 
wastes or degenerates. The degenerated fibers can be dis- 
tinguished by their appearance under the microscope, espe- 
cially if treated with special straining reagents. (2) By 
noticing the growth of the nerve fibers in the embryo (the 
embryological method). (3) By the different parts of nerv- 
ous impulses by electrical charges. The tracts may thus be 
grouped into two classes: those which degenerate below the 
cut or injury (lesion) in the cord, known as descending de- 
generation, and those which degenerate above the lesion, 
known as ascending degeneration. 

The principal tracts or columns of descending degen- 
eration are, — 

1. The Crossed Pyramidal Tract. — This is found in the 
lateral column at the outer part of the posterior horn of gray 
matter throughout the length of the cord. This tract con- 
sists of rather large fibers mingled with smaller ones. It 
descends from the opposite side of the cortex of the brain, 
the fibers crossing at the pyramids of the medulla (Fig. 56). 

2. The Direct Pyramidal Tract. — It is situated in the 
anterior column (Fig. 56), by the side of the anterior median 
fissure. Its fibers are of large size. It gradually diminishes 
in size on passing downward, ending near the middle of the 
dorsal region. It may belong to a portion of the crossed 
pyramidal tract, the fibers not crossing {decussating) in the 
medulla, but passing probably to the opposite side in the 
cord itself, through the anterior white commissure. 

3. The Antero-lateral Descending Tract.— This tract is sit- 
uated in the antero-lateral column. Its fibers are connected 
with cells in the brain cortex on the same side as that of 
the column. 



THE SPINAL CORD. 



99 



4. The Comma Descending Tract. — This is a small tract 
in the upper part of the cord, in the middle of the postero- 
lateral column. It is uncertain whether its fibers originate 
from cells higher up in the cord or from the descending fibers 
of the posterior root. 

The principal tracts of 
ascending degeneration are : 

1. The Antero-lateral of 
Gowers. — This is situated 
at the outer part of the cord 
(Fig. 56), and mingles 
with the corresponding de- 
scending tract. Its fibers 
can be traced upward to the 
cerebellum. They probably 
have their origin in cells 
in the posterior cornu of 
the cord. 

2. The Direct Ascending 
Cerebellum Tract. — This 
tract is situated at the outer 
part of the cord, external 
to the crossed pyramidal 
tract in the dorsal and cer- 
vical regions. Its fibers 

-nrnVmhlv arkp -from thp of spinal cord. 2. Posterior root of spinal 
prOOaOlV arise IlOm tne ner £ e 3 Posterior ganglion. 4. Anterior 

flviVpvlinrW -nrn^p^pq of norn ot £ ra y matter. 5. Anterior root of 
dXlb c\ miuer procebbeb o_l spinal ner ve. 6. Posterior division. 7. 

tliA ppIU rvf PlctrVp'o r>r»l External branch. 8. Posterior cutaneous 
LUfcJ ceiib Ul V^ldiAe b cui branC h. 9 Anterior division of intercostal 

nerve. 10. Recurrent nerve. 11. Ramus 

limn. communicans. 12. Sympathetic ganglion. 

9 Tli p Pnc+Arn lo+prol Ac 13- Ramus efferens. 14. Lateral cutaneous 

6. ine rOSierO-iaterai AS- branch. 15. Posterior branch. 16. An- 

^A-n^iTur Trar>T r\r Pnlnm-n nf terior branch. 17. Anterior cutaneous 

Cenamg iract, Or lOiumn 01 nerve . (Modified from Henle.) 

Burdach. — This is situated 

between the superficial postero-lateral tract and the comma 
tract (Fig. 56). It is chiefly composed of large fibers that 
are continuous with the fibers of the entering posterior roots, 
and after passing for some distance in the cord, numerous 
filaments pass off into the gray matter. 

L. r -'• 




Fig. 57. 



Distribution of Spinal 
Nerves. 



1. Posterior horn (cornu) of gray matter 



100 THE NERVOUS SYSTEM. 

4. The Posterio-mesial Tract, or Column of Goll This 

is situated in the area (Fig. 56) between the posterior median 
fissure and the column of Burdach. The fine fibers of which 
it is composed are derived from the posterior root fibers, and 
pass up this column into the medulla, where they end among 
cells of the nucleus gracilis. 

5. The Tract of Lissauer.— This is a small tract, close to 
the posterior root, from which its fine fibers are derived. 

The Spinal Nerves. — In our dissection of the spinal cord 
we found thread-like bodies {nerves) attached to the spinal 
cord. These are the spinal nerves. They are arranged in 
pairs. They originate by two roots, one from the posterior 
part of the cord, the 'posterior root; the other from the 
anterior part of the cord, the anterior root. The two roots 
pass through separate openings in the dura mater, but unite 
before passing through the vertebral foramen to form a 
mixed nerve, from which branches are given off to the dorsal 
and ventral parts of the body, as well as a visceral branch 
{ramus communicans) to the sympathetic system (Fig. 57). 

Before the roots unite, a ganglion is found on the pos- 
terior root, where the roots lie in the intervertebral foramen. 
By experimental excitation of the fibers of the posterior 
root it is shown that it contains nerves which go to the spinal 
cord {afferent), while similarly the anterior root is shown to 
contain nerves which come from the cord {efferent). The 
anterior also contains a few afferent fibers, but the posterior 
is entirely afferent or sensory. 

The anterior roots arise, by several converging bundles 
of fibers, from the anterior column of white matter ; and on 
tracing the fibers into the gray matter of the cord many of 
them are found to be continuous with the axis-cylinder proc- 
esses of the large cells in the anterior horn. These fibers 
go from the cord to the skeletal muscles, and are called motor 
fibers, as they carry stimulus for muscular contraction. 
Some of the fibers pass by these cells, and do not appear to 
be connected with them. The exact origin of these fibers 
has not been clearly determined, but some pass to the 



THE SPINAL NERVES. 



101 



white commissure, and probably have their origin in the 
cells of the anterior horn of the other side. Some of 
these pass to the posterior horn. The anterior root con- 
tains, besides the motor fibers to the skeletal muscles, vaso- 
motor and secretory fibers. The posterior fibers enter the 
cord in a more compact mass than the anterior fibers, and 
after their entrance into the cord, separate into two sets. 
The first consists of somewhat large fibers, and passes into 
the postero-lateral white column, 
proceeding for the most part up- 
ward, and entering either the pos- 
terior median tract or the adjacent 
gray matter, and some continue 
on through the gray matter to the 
anterior horn. 

The second or small fibers 
enter at the tip of the posterior 
horn, and join the ascending fibers 
in the tract of Lissauer. As the 
fibers of the posterior root enter 
the cord, they divide into two 
principal branches, running up- 

_ i -i -i i • i . 1 - Anterior meaian nssure. z 

V am and downward m this UOS- Posterior root. 3. Anterior root 
«.«_J~ L'j. n , 4. Spinal ganglion (posterior). 5 

teiior Wmte COllimn, or the ad- Antero-lateral fissure. 

jacent posterior horn, and give off collateral branches, which 
run inward toward the gray matter, and end in a network 
of fibrils around the nerve cells. The fibers of the posterior 
root originate in the cells of the posterior root ganglion. A 
longitudinal section of this ganglion shows it to consist of 
a number of cells with nerve fibers passing through them. 
Most of these cells are pear-shaped and unipolar, and the 
cell process joins the traversing nerve fiber by a T-shaped 
union, though it is possible that some fibers may pass through 
without any connection with a cell. 

Section of the root between the ganglion and the cord 
leads to the degeneration of the central part, or the part in 
connection with the cord ; while the peripheral part, or the 




Fig. 58.— Origin of Spinal 

Nerves. 
1. Anterior median fissure. 2. 



102 THE NERVOUS SYSTEM. 

part in connection with the ganglion, remains unaffected. 
Section below the ganglion leads to waste in the peripheral 
part, but not in the central part. Section of the anterior 
root leads to degeneration in the peripheral part, but not in 
the central part. From this we learn that the center of 
nutrition (trophic center) for the sensory or posterior fibers, 
is the posterior ganglion ; that for the motor anterior fibers, 
the cells of the gray matter of the cord. There are few fibers, 
however, which remain unaffected in the peripheral end of 
a cut anterior root, the end containing a few degenerate 
fibers among the mass of unaffected ones. These are known 
as the recurrent sensory fibers. If the anterior root of a 
spinal nerve be divided, and the peripheral end stimulated, 
there is not only movement of the muscles supplied by the 
nerve, but in some cases there are evidences of pain. This is 
called recurrent sensibility. This is caused by a few sensory 
fibers which leave the cord by the posterior roots, but turn 
back into the anterior root. By dividing the posterior root, 
recurrent sensibility disappears. 

"There are thirty-one pairs of spinal nerves. The spina] 
cord is regarded as a series of segments, each segment corre- 
sponding to a pair of nerves. Each segment of this ground- 
work consists of a central mass of gray matter connected on 
each side with an anterior and a posterior root, thus forming 
a segmental nervous mechanism. By some, the spinal seg- 
ment has been compared to ganglion. A ganglion and the 
gray matter of a spinal segment both contain nerve cells, but 
with few exceptions they have little or no resemblance. Their 
structure compared is as follows : — 

1. In a ganglion the constituent nerve cell is a develop- 
ment of the axis-cylinder of a fiber into a nucleated cell body, 
which lies on tfre course of a fiber, or where the fiber divides 
into two or more; and we have evidence that the nucleus, 
with its cell substance, exercises an important influence on 
the nutrition of the nerve fiber and its functional activity. 
But we have no satisfactory evidence that the cell can auto- 
matically originate nervous impulses, or exercise any marked 



FUNCTIONS OF THE SPINAL CORD 103 

transforming power over the impulses passing along the fiber. 
The gray matter of the spinal segment is especially possessed 
of the reflex and automatic, as well as other powers. 

2. In a ganglion the nerve fibers may divide, and in small 
peripheral ganglia the divisions may give rise to very deli- 
cate fibrils ; but the fibers or fibrils resulting from the division 
leave the ganglion to follow their appropriate courses. In 
the spinal cord, both efferent and afferent fibers divide in 
such a way that their divisions are lost to view in the gray 
matter. All the processes, except the axis-cylinder process, 
divide into branches, and seem to end in nervous fibrils, lost 
to view in the gray matter. While our knowledge of the 
junction of the posterior root is imperfect, what we know 
leads us to believe that the fibers of the posterior root, either 
by the means of cells or by direct division of the axis-cylinder, 
break up into fibers which are lost in the gray matter. We 
have evidence that the anterior and posterior roots are con- 
tinuous, not by a gross continuation of the axis-cylinder, but 
in a peculiar way through the divisions of branches of nerve 
cells or axis-cylinders, forming a nervous network: while 
the fibers are not continuous histologically, they are so func- 
tionally. 

Functions of the Spinal Cord. — The spinal cord is both 
a conductor of nerve impulses and a center of reflex and auto- 
matic action. By means of its fibers it has connection with 
the body, and by means of its relation to the brain acts as the 
great conductor of afferent impulses to the brain, where they 
may be perceived, and the impulses sent back by the cord to 
the afferent fibers. We should bear in mind that there is no 
continuous nerve fiber running from the end organ to the 
cells of the brain by means of the spinal cord, and an efferent 
fiber returning from the cells of the brain by means of the 
cord to the muscle or gland to be stimulated (as some of us 
have been taught), for this is not true. There is a line of 
communication, the plan of which we shall soon learn. 

It serves also as a trophic center for the efferent nerves, 
and as a center of automatic and reflex action, 



104 THE NERVOUS SYSTEM. 

By experiment and observation the paths of the sensory 
and motor impulses have been made out ; while not perfectly 
determined, yet they have been sufficiently so to aid us very 
much in learning the paths which the afferent and efferent 
impulses take. 

1. Paths of Sensory Impulses of the Cord. — Afferent 
impulses find their way to the cord by the posterior root, and 
pass up some or all of the ascending tracts, i. e., of ascend- 
ing degeneration to the brain. But the tract taken by the 
different impulses has not been definitely determined. 
Recent experiments have, however, definitely proved that 
all sensory impulses do not decussate or cross over in the 
cord, as was formerly supposed, but that they pass up the 
same side for the most part, and cross chiefly in the medulla 
to reach the opposite side of the brain. Mott thinks that 
impulses of touch, pressure, and the muscular sense pass 
up the same side, but that sensations of pain pass up both 
sides. 

2. Paths of Motor Impulses in the Cord. — Efferent im- 
pulses pass from the brain along the two pyramidal tracts, 
for the greater part in the crossed pyramidal, these tracts 
being undoubtedly the channels of voluntary impulses. For 
the most part they originate in the cortex of the cerebrum 
at one side, in the pyramidal decussation in the medulla. A 
few fibers do not cross in the medulla, but pass down in the 
direct pyramidal tract to decussate in the cord by the anterior 
white commissure. The vasomotor impulses to the limbs 
travel along the lateral columns of the cord on the same side. 1 

i By section (cutting the cord entirely across) and hemisection (cutting the 
cord half across), we learn that,— 

1. Complete transverse section of the spinal cord leads to,— 

(a) Loss of motion of the parts supplied by the nerves, below the section, on 
both sides of the body. 

(b) Loss of sensation in the same regions. 

(c) Degeneration, ascending and descending on both sides of the cord. 

2. Hemisection leads to,— 

(a) Loss of motion of the parts supplied by the nerves below the section on 
the same side of the body as the injury. 

(b) Loss of sensation in the same region. The loss of sensation is not a very 
prominent symptom, and is limited to the sense of localization and to the muscu- 
lar sense. The animal can still feel sensation of pain, and of heat and cold. 

(c) Degeneration, ascending and descending nearly entirely confined to the 
same side of the cord as the injury. 



REFLEX ACTION OF SPINAL CORD. 



105 



Reflex and Automatic Action of the Spinal Cord. — In 

vertebrate animals, and especially in man, the central nerv- 
ous system (cerebrospinal) contains, in addition to nerve 
fibers, a number of nerve centers, localized in certain parts, 
vet having the power of influencing each other. They do 
not have direct connection by means of nerve fibers, as was 
once thought, but rather their cells, by means of their 
branches, and also 
by reason of the 
molecular ground- 
work of the cord, 
are so related that 
the excitation of one 
may affect the other, 
as we shall learn 
later on. These cen- 
ters of the brain and 
spinal cord may be 
regarded as forming 
connected groups of 
cells endowed with 
the power of regulat- 
ing some function of 
the bodv. Thus we 

. . horn of gray matter. 4. Connection with anterior 

have a respiratory horn. 5. Anterior horn. 6. Efferent, or motor, fibers. 
" 7. Muscle. (Notice in this case there is a direct 
Center, a Vasomotor connection between parts.) 

center, a control center, tonic centers, and a perspiratory 
center. 1 

Physiologically speaking, the whole process of the nerv- 
ous system may be spoken of as automatic, reflex, or psychic. 

In reflex action we have the immediate efferent response 
independent of the will; i. e., these centers have the power 
to respond to afferent impulses. The spinal cord may be con- 
sidered as made up of a number of these centers. It should 
be remembered that any part of the brain may act as a reflex 
center. Especially is this true of the medulla or bulb. 

1 It is proper to say that this explanation of the facts is not accepted by aU 
physiologists. See J. Loeb's " Physiology of the Brain " for other views. 




1 r 

Fig. 59.— Old Idea of Reflex Action. 
1. Sense organ. 2. Sensory nerve. 3. Posterior 



106 THE NERVOUS SYSTEM. 

The mechanism of reflex action may consist of the fol- 
lowing parts: (1) A sentient surface or peripheral sense 
organ; (2) from these an afferent tract to the reflex center; 

(3) connection of the reflex center with efferent tracts; (4) 
a muscle, gland, secreting cell to receive the efferent impulse. 
These form what is called a reflex arc (Fig. 60). 

The old idea as to the manner in which it takes place is 
as follows: (1) A sensory nerve fiber is stimulated (Fig. 
59) ; (2) the impulse is carried by an afferent fiber to a 
sensory nerve cell; (3) then transmitted to a motor nerve 
cell by branching processes connecting the two (Fig. 60) ; 

(4) and these are then reflected down the motor nerve fibers 
(efferent) to the muscle or gland which it excites. 

In order to understand the present notion it will be 
necessary for us to consider the present idea of the structure 
of the nervous system. The study of the nervous system by 
the method introduced by Golgi has led to some new concep- 
tions as to its structure (see Appendix). " The whole nerv- 
ous system consists of nerve cells and their branches, sup- 
ported by neuroglia in the central nervous system, and by 
connective tissue in the nerves. Some of the branches of a 
nerve cell break up almost immediately into smaller branches, 
ending in an arborescence, or fine twigs ; these branches are 
called dendrons, and the fine twigs dendrites; one branch 
becomes the long axis-cylinder of a nerve fiber. This large 
branch is called the axis-cylinder, or neuraxon. By most 
writers the term neuron is applied to the complete nerve- 
unit (Fig. 84), which consists of the body of the cell and 
all its branches. It has been supposed by some observers 
that the axis-cylinder process is the only one that conducts 
nerve impulses, the dendrons being rootlets to imbibe nutri- 
ment for the nerve cell. This conclusion has not, however, 
been generally accepted. The dendrons may be nutritive, 
but it is believed that they also, like the rest of the nerve 
units, are concerned in the conduction of nerve impulses. 
A strong piece of evidence in this direction is the fact that 
the fibrils of the axis-cylinder may be traced through the 
body of the cell into the dendrons, 



REFLEX ACTION OF SPINAL NERVES. 



107 



It is essential that we keep in mind the fact that eacli 
nerve unit (neuron) is anatomically independent of every 
other nerve unit. There is no anastomosis of the branches 
of one nerve cell with those of another; the branches inter- 
lace and intermingle, and nerve impulses are transmitted 
from one nerve unit to another, but not by continuous struc- 
ture. The structures are contiguous, but not continuous. 

According 
to this view, 
reflex action 
takes place 
a s follows : 
( 1 ) Excita- 
t i o n occurs 
at the sen- 
sory nerve 
fibers ; ( 2 ) 
the impulse 
i s transmit- 
ted by the 
sensory 
nerve fiber to 
the nerve 

center, where Fig. 60 — Mechanism of Reflex Action. 

it P-nrlc -nnt 1. Gray matter of spinal cord. 2. Anterior horn. 3. Posterior 
iu eiius, nut h orrK 4, Sensory collateral joining the motor cells directly, 
in +Vio T.QTTTfl &• Motor collaterals joined to a cell. 6. Cell joining with 
m ine nerve collateral (4). 7. Sensory collateral fibers. 8. Sensory, or 
11 V. + l afferent, nerves. 9. Posterior ganglion. 10. Motor, or afferent, 
Cell, DUt Dy nerve (and cells). 11. Sense organ. 12. Muscle. When the 

b course is from 11, 8 to 4 and across to 10 and 12, it is called 

O r 1 Z - direct reflex; when through 11, 8, 7, 6, and 5 across to 10 and 21, 
-, indirect reflex. (Modified from Henle.) 

mg around a 

nerre cell and its dendrons. The only nerve cell in actual 
continuity with the sensory nerve fiber is the one in the 
spinal ganglion from which it grew. (3) While the terminal 
arborization of the sensory nerve fiber interlaces with the 
motor nerve cell, yet by this contiguity, or touching, the 
motor nerve cell sends an impulse by its axis-cylinder process 
to the muscle. 

In such animals as the frog, the cord alone can carry out 




108 THE NERVOUS SYSTEM. 

numerous reflex acts, some of which may be very complex. 
After the brain has been removed from a frog, it recovers 
from the shock in about an hour ; and if protected from any 
stimulating influence, remains still until it dies. But if a 
stimulus be applied to the skin of one foot, that foot will 
draw up. This is an example of a single reflex action, and 
illustrates what is often called the law of unilateral reflection. 
Generally a slight excitation of a sensitive region causes a 
reflex movement in the neighboring muscles. A stronger 
stimulus not only leads to a movement of the same side, but 
to a less degree in the opposite side also. If the stimulus 
be very strong, or if the cord be in a very excitable condition, 
the sensory impulse may be reflected along most of the motor 
nerves, producing what is called a reflex spasm. This spread- 
ing has been called the law of radiation or diffusion. Some 
drugs, as strychnine, so affect the gray matter of the spinal 
cord, that the slightest touch on the skin puts all the muscles 
into a state of spasmodic contraction. When one of the toes 
of a brainless frog is dipped into diluted sulphuric acid, the 
leg is not drawn up for some time. 

From this we may learn that a weak impulse may not 
itself be capable of producing a reflex act, buf that a succes- 
sion of such impulses sent to the cord may combine their 
influence until a movement is caused. This is known as a 
summation of stimuli. 

The stimulation of the flank of a frog with acid causes 
the leg of the same side to be swept over the spot; and if 
this leg be held, the other leg tries to remove the irritation. 
So well directed are these movements, that at first sight they 
seem to be acts of intelligence, but a more careful view shows 
that they are mechanical, as is shown by the fact that a 
decapitated snake will coil around a red-hot iron as readily 
as around a stick in contact with its body. These actions 
call for complicated movements involving groups of muscles 
requiring complex co-ordination. The movements seem to be 
protective or purposive in character. 

From these and similar experiments we learn that excita- 



a • 

F'S- 

o 

s>»3 



"»5 






^ CJJ 



E,cna 



a 



O S O ** 

c ° 3-2. 

— . X 
«k.0B 

s Fa 
§3' 



s /■ a 

a '■ 



"g O B 

III 





AUTOMATIC ACTION. 109 

tion of the cord in many parts thus tends to spread in various 
directions, but with a preference for certain paths marked 
out by the structure and habits of the cord. Keflex action 
occurs more readily in a brainless frog than in one whose 
brain has not been removed. The reason for this seems to 
be that the brain exercises an inhibitory power over the cord, 
thus restricting its activity. This inhibitory power is nicely 
illustrated by the great ease with which reflex action occurs, 
and by the absence for a time of any sense of pain to a soldier 
wounded in battle, when his mental energies are all centered 
on the fight. If the knee be half bent, and tapped sharply on 
the patella tendon, the rectus muscle of the thigh contracts, 
and raises the leg. This action is called tendon reflex. 

This " knee jerk," as it is called, is present in health, 
but absent or exaggerated in some diseases, as those of the 
cord; it is therefore of great importance in aiding the phy- 
sician in determining certain diseases. There is doubt as to 
this being a true reflex action, as the time between the blow 
and the contraction is not as short as in muscular contrac- 
tion. The cutting of the nerve, coming to this muscle from 
the cord, destroys the action. 

The time required for any reflex act varies much with 
the strength of the stimulus, being less for strong stimuli. 
The velocity varies also with the condition of the cord, being 
much slower when the cord is exhausted, and in case of dis- 
ease. The time for reflex action has been estimated at from 
.01 to .06 of a second. 

Automatic Action of the Spinal Cord. — Foster defines 
automatic action as an action which appears to be not imme- 
diately due to any change in the circumstances in which the 
organ or body is placed, but to be the result of changes aris- 
ing in the organ or body itself, and determined by causes 
other than the influence of the circumstances of the moment. 

Some automatic actions are of a continued character; 
others repeated in regular rhythm, as the beating of the 
heart ; others still very irregular and variable, as those auto- 
matic actions we attribute to the will. 



110 THE NERVOUS SYSTEM. 

We have an illustration of this automatic action in the 
rhythmic beat of the heart and the rhythmic discharge of 
the respiratory impulse. While these are not due to the 
changes taking place in the cord, they serve well to illustrate 
the nature of automatic action. In automatic power the 
brain surpasses the cord. 

One of the most marked cases of the automatic action of 
the cord is the maintaining of the muscular tone of the skel- 
etal muscles. While this automatic action is not caused 
directly by afferent impulses, it is greatly influenced by 
them, in that they bring about a greater intrinsic change in 
the centers which are the causes of the automatic action. 
We can thus account for the greater automatic action of the 
brain. The cause of this automatic action is due to the me- 
tabolism of the nerve tissue, anabolism, or building up of the 
explosive, being followed by katabolism, or its discharge. 

THE BRAIN. 

That part of the cerebrospinal system contained in the 
cranial cavity is called the brain, or encephalon. 

Weight of the Brain. — The brain of the average adult 
human female weighs 44.5 ounces, and that of the male, 49.75 
ounces. Cases are recorded in which the brain attained a 
weight of 74.8 ounces, one such case being that of an idiot 
boy. In the European, the average maximum weight is 
reached between the thirtieth and fortieth years. The mini- 
mum weight in the European is 34.39 ounces in the female, 
and 39.96 ounces in males. 

The weight of the brain of a gorilla was found by Pro- 
fessor Owen to be fifteen ounces. In the healthy body the 
relation of the weight of the human brain to that of the body 
is as one to forty-one. 

Parts of the Brain. — Its principal parts are: (1) The 
large mass above and in front, the cerebrum; (2) the smaller 
mass to the rear and beneath the cerebrum, the cerebellum; 
(3) the club-shaped body just in front of the cerebellum, 
and which seems to be the continuation of the spinal cord, 



STRUCTURE OF THE BRAIN. 



Ill 



tlie medulla oblongata, or bulb, and overlying as seen from 
the ventral surface, the cerebellum; (4) the quadrate mass 
just above the medulla, showing transverse fibers connect- 
ing it externally with the two sides of the cerebrum, the pons 
Varolii. Internally, it is found to be continuous with the 
medulla. 

The striated bundles of nervous matter emerging from 

22 £3 




13 12 11 10 9 8 7 6 

Fig. 61.— Section of Cranium and Brain on Median Line. 

1. Septum lucidum. 2. Foramen of Monro. 3. Anterior commissure. 4. 
Lamina terminalis. 5. Corpus callosum. 6. Chiasma. 7. Pituitary body. 8. 
Corpora mammillaria. 9. Pons. 10. Sulsus hypothalam. 11. Medulla. 12. Lam- 
ina quadrigemina. 13. Pineal gland. 14. Cerebellum. 15. Transverse sinus. 
16. Tentorium. 17. Calcarine fissure. 18. Cuneus. 19. Parieto-occipital fissure. 
20. Precuneus (quadrate lobe). 21. Sup. sagittal sinus. 22. Corpus callosum (pos- 
terior). 23. Choroid plexus. 24. Fornix. 25. Middle commissure. 

the pons and entering the under part of each cerebral hemi- 
sphere as they diverge, are the crura cerebri. 

The small triangular plate of brain tissue traversed by 
many arteries, and lying between the diverging peduncles 
of the crura, is called the posterior perforated space. The 
two small white bodies near by, the function of which is 
unknown, are the corpora albicantia. 



112 



THE BRAIN. 



The tuber cinereum is a small eminence of gray matter 
situated in front of the corpora albicantia, attached to the 
junction of the optic nerves, which is called the optic com- 
missure. The hollow conical process passing from the tuber 




Fig. 62. — Inferior Surface of Brain. 

1. Corpus callosum (genu). 2. Gyrus subcallosus. 3. Anterior perforated space. 
4. Optic tract. 5. Fissure of Sylvius. 6. Corpora mammillaria. 7. Gyrus 
hippocampus. 8. Tegmentum. 9. Orus cerebri. 10. Substantia alba. 11. Me- 
dulla oblongata. 12. Pons. 13. Thalamus. 14. Posterior perforated space. 15. 
Limen insulae. 16. Island of Rail. 17. Tuber cinereum. 18. Origin of olfactory 
lobe. 19. Lamin. termin. 20. Olfactory bulb. 

Roman numbers refer to the pairs of cranial nerves. I. Olfactory. II. 
Optic, etc. See page 127. 

cinereum to the small, reddish body is the infundibulum. 
The small, red body is called the pituitary body, and is of 
unknown function. Unless the dissection has been carefully 
made, the pituitary body will be removed with the dura mater, 
as it is inclosed in this membrane. 

The club-shaped masses of gray matter lying in the 
grooves on the under surface of the frontal lobes of the 



STRUCTURE OF THE BRAIN. 



113 



cerebrum and on each, side of the fissure (median or longi- 
tudinal fissure), are the olfactory tracts and bulbs. 

To learn of the internal structure, we make section of 
the brain in various directions. Fig. 61 represents a sec- 
tion made on the median line from above downward. By a 
careful study of Figs. 61, 63, 64, 65, and 66, and a com- 
parison with the 
dissections that 
have been made, 
a good idea of the 
general structure 
of the brain may 
be had. 

As we have 
seen, the spinal 
cord is continuous 
with the medulla, 
becoming the me- 
dulla at the large 
opening (foramen 
magnum) in the 
base of the skull. 
The central canal, 
which we found 
traversed the en- 
tire length of the 
spinal cord, 
widens on enter- 
ing the medulla, 
into a lozenge-shaped cavity called the fourth ventricle. 

The cerebellum overhangs the fourth ventricle. The pe- 
culiar tree-like appearance of the cerebellum on section, due 
to the arrangement of the white matter, is called the arbor 
vitte. The fibers of the medulla pass upward, and cross into 
the pons Varolii, beyond which will be seen the crura cerebri. 

The four hemispherical masses situated in the upper and 
back part of the crura cerebri, from which they are separated 
8 




11 10 

Fig. 63.— Superior Surface of Brain. 
1. Longitudinal fissure. 2. Occipital convolution. 
3. Interparietal fissure. 4. Superior parietal lobe. 5. 
Posterior central fissure. 6. Posterior central con- 
volution. 7. Central fissure. 8. Anterior central 
convolution. 9. Anterior central fissure. 10. Median 
frontal convolution. 11. Superior frontal convolu- 
tion. 



114 



THE BRAIN. 



by a small channel passing from the fourth ventricle, are 
the corpora quadrigemina, two of which may be seen in 
Fig. G6. 

Just above these is a small cone-shaped body, the pineal 
gland. It may be of interest for us to know that by some 
scientists this is thought to be the remnant of a third eye, 
and also that some psychologists have considered it as the 

seat of consciousness. 
Of its true function, 
however, nothing is 
known. The small 
channel which leads 
from the fourth to 
the third ventricle is 
the aqua?ductus . Syl- 
vii. The third ven- 
tricle is a narrow 
median cavity, 
bounded on each side 
by the internal sur- 
face of an oval mass 
of matter that pro- 
jects internally, 
known as the optic 
thalamus (Fig. $6). 
The third ventricle 
thus lies between the optic thalami, and the gray matter of 
the thalami being connected across the narrow cavity by the 
soft commissure. In the roof of the third ventricle is the 
fornix, which is covered by a double fold of the pia mater, 
called the velum interpositum. The fornix is a longitudinal 
arch of white fibrous matter united to the corpus callosum 
behind and in front to a thin partition, the septum lucidum 
(Fig. 65). The space between the two layers is called the 
fifth ventricle. The fifth ventricle has no connection with 
the other ventricles, and is not regarded as a true ventricle. 
All the other ventricles are in communication, and contain a 




Fig. 64. — Oast of the Ventricles op the 

Brain. 
1. Recess of the ^pineal gland. 2. Fissure of 
hypothal Monroi. 3. Third ventricle. 4. .Lateral 
ventricle. 5. Anterior horn of lateral ventricle. 
6. Foramen of Monro. 7. Optic recess. 8. Recess 
of inf undibulum. 9. Inferior horn of lateral ven- 
tricle. 10. Fourth ventricle. 11. Lateral recess 
of rhomboid fossa. 12. Foramen of Magendie. 13. 
Aqueduct of Sylvius. 14. Posterior horn of lateral 
ventricle. 



STRUCTURE OF THE BRAIN. 



115 



small quantity of fluid (the cerebrospinal). The fornix (Fig. 
65) descends to the base of the brain. On each side from 
the front part of the third ventricle an aperture (the foramen 
of Monro) (Fig. 64) leads by a G-shaped connection to the 
lateral ventricle in each cerebral hemisphere. These may be 
brought to view by slicing a brain horizontally down to the 
corpus callosum (Fig. 65), and removing it sufficiently. 
Each lateral 



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Fig. 65. 



11 10 9 

Transverse Vertical, Section of 
the Brain. 



ventricle is an ir- 
regula rly c u r v e d 
cavity, extending 
in the substance of 
the corresponding 
cerebral hem- 
isphere for about 
two thirds of its 
length. It % is lined, 
as are all the true 
brain ventricles, 
by ciliated epi- 
thelium. Each of 

, 1 , 1. Median longitudinal stria. 2- Corpus callosum. 

the lateral ven- 3. Caudate nucleus. 4. Internal capsule. 5 and 6. 

. Lenticular nucleus. 7. External capsule. 8. Tempo- 

tricles Consists of ral lobe. 9. Optic chiasma. 10. Optic recess. 11. Pia 

mater. 12. Anterior perforated space. 13. Anterior 

a Central cavitV Or commissure. 14. Olaustrum. 15. Pillar of fornix. 16. 

" ' Septum lucidum (pellucidum). 

body, and three 

small cavities, or cornua; the body of each lateral ven- 
tricle is separated in front from its fellow by the septum 
lucidum. The roof of each of these ventricles is formed 
mainly by the under surface of the corpus callosum. The 
rounded mass of nervous matter in the front part of the floor 
of each of these ventricles is called the caudate nucleus of 
the corpus striatum. The deeper part of the corpus stri- 
atum, the lenticular nucleus, is imbedded in the mass of 
each cerebral hemisphere. There is also found in the lateral 
ventricles a part of the upper surface of the optic thalamus, 
the inner sides forming the lateral boundaries of the third 
ventricle. Each thalamus rests upon and is connected with 



116 



THE BRAIN. 



one of the crura cerebri, and has on its outer and hindermost 
part two small elevations, called the corpora gendculata. A 
tract of white fibers (the internal capsule) continuous with 
the lower or anterior portion of the cms, and lying between 

the lenticular nu- 
cleus on the outer 
side and, the optic 
thalamus and cau- 
date nucleus on the 
inner side, passes 
upward to the outer 
layer (cortex) of the 
cerebrum, some of 
its fibers diverging 
on the way, forming 
a fan-shaped mass of 
white, the corona 
radiata. 

The cerebral hem- 
isphere, two ovoid 
masses separated by 
the median fissure, 
and connected by the 
corpus' callosum, 
makes up about seven 
eighths of the mass 
of the brain. The 
surface of the cere- 
brum is molded into 
eminences, which 
form convolutions, 
or g y r i , separated 
from each other by small fissures, or sulci. The depressions 
on the surface mark off each hemisphere into five lobes: 
frontal, parietal, occipital, temporo-sphenoidal, and central, 
or island of Reil. For the names of the fissures and the rela- 
tion of these lobes, see Fig. 76. 




Fig. 66. — 1. Corpus callosum. 2. Caudate 
nucleus. 3. Septum lucidum. 4. Pillar of fornix. 
5. Stria termin. 6. Tubercle of superior thalamus. 
7. Median commissure. 8. Peduncle of Pineal 
gland. 9. Optic thalamus. 10. Triangle of the pe- 
rt uncle of the pineal gland. 11. Pulvinar. 12. 
Posterior commissure. 13. Pineal gland. 



Covering of the) brain. 117 

Like the other portions of the nervous system, the brain 
consists of gray and white matter, all of its parts being more 
or less connected, by numerous fibers. 

The gray matter is similar in structure to that of the 
spinal cord, consisting of nerve cells, neuroglia, and minute 
blood vessels. It is found principally (1) on the surface 
(cortex) of the brain, (2) in special areas throughout the 
substance of the brain, (3) lining the ventricles, and (4) in 
the ganglia and bodies; as, the olfactory lobes, corpora 
striata, optic thalami, corpora quadrigemina at the base of 
the brain. The white matter consists of fibers of various 
sizes medullated, but without the primitive sheath, and 
arranged in bundles separated by neuroglia. These fibers 
may be arranged into three systems by the direction they take : 
(1) Diverging or peduncular fibers (projection fibers), 
which connect the hemispheres with the lower portions of 
the brain and the cord, and which are in a great measure 
direct prolongations of the axis cylinders of the nerve cells of 
the cortex; (2) transverse, or commissure fibers (including 
the fibers of the corpus callosum, and the anterior and pos- 
terior commissures), which connect the two hemispheres; 
(3) associated fibers, which connect different structures of 
the same hemispheres. (See Fig. 73.) 

The Covering of the Brain. — The brain, like the spinal 
cord, is invested by three membranes (Fig. 67) or meninges: 
the dura mater, the pia mater, and the arachnoid membrane. 

The dura mater, the external one, is a dense, fibrous mem- 
brane closely attached to the inner surface of the skull, form- 
ing the periosteum for the inner surface of the' bones of the 
cranium. It is continuous with the dura mater, that forms 
the outer coat of the cord, and it becomes intimately attached 
to the bony cavity of the skull before passing through the 
foramen magnum. On reaching the skull, it divides into 
two layers, and at various places the two layers separate to 
form channels, or sinuses, for venous blood. This membrane 
also sends off three processes, or membranous partitions: (1) 
The falx cerebri, which lies vertically between the two hemi- 



118 



THE BRAIN. 



spheres in the median fissure; (2) the tentorium cerebelli 
(Fig. 67), forming a sloping vaulted partition at the back 
between the cerebrum and the cerebellum; (3) the small falx 
cerebelli between the hemispheres of the cerebellum. 

The pia mater is the membrane which directly invests 
the brain, dipping down into its fissures and sulci. It is 
fibrous, delicate, and vascular. From its surface numerous 
small blood vessels pass into the brain substance. At the 




Fig. 67. A. — Covering of the Brain. 

Section through portion of cranial bone and upper surface of brain. 1. Cranial 
bone. 2. Cerebrum. 3. Dura mater. 4. Subdural space. 5. Arachnoid mem- 
brane. 6. Subarachnoid space. 7. Pia mater. 8. Vein from diploe. 9. Subdural 
process. 10. Sagittal sinus. 11. Lateral sinus. 

transverse fissure it is prolonged into the lateral ventricles, 
and over the third ventricle forming the triangular fold of 
the pia mater lying just beneath the fornix (Fig. 67), where 
it can be seen when the fornix is cut through and raised, and 
also the choroid plexuses. The fourth ventricle also receives 
a prolongation over its posterior roof. 

Lying just outside of the pia mater is the arachnoid, the 
most delicate of the coverings of the brain. It does not so 
closely invest the brain as does the pia mater, as it passes 
over the fissures and sulci without dipping down into them. 
There is a space between the dura mater and the arachnoid, 
known as the subarachnoid space. It is not uniform in size, 
its course being at the base of the brain much widened. As 
in the spinal cord, thin bands of connective tissue connect 
the pia mater and arachnoid, and in the meshes of the sub- 
arachnoid space thus formed is the cerebrospinal fluid. The 



THE MEDULLA OBLONGATA. 119 

subarachnoid space communicates with the ventricles of the 
brain and the central canal by a small hole in the pia mater 
of the roof of the fourth ventricle, called the foramen of 
Magendie. 

The Medulla Oblongata, or Bulb.— This is the bond be- 
tween the spinal cord and the brain proper. It is by means 
of the bulb that the shifting of the white fibers of the cord 
takes place, many of the fibers crossing (decussating) over 
to the opposite side. As we 
have seen, the narrow central 
canal of the cord widens out 
into the wide fourth ventricle 
(Fig. 6-1) on the posterior sur- 
face. The gray matter of the 
cord becomes separated into 
four masses on each side by the 
passage of fibers across the an- 
terior and posterior horns. 

There is also additional gray 

.. .. n mi ° Fig. 67. B. — Covering of the 

matter superadded. Inere are brain. 

, /» rn i*i Vertical section through cranial 

tWO tracts 01 IlberS WniCll Can cavity and brain. 1. Superior sagit- 
', , , t ., -, ., tal sinus. 2. Petrosal sinus. 3. Bas- 

be Clearly traced through the ilary artery. 4. Falx cerebri. 5. Ten- 
bulb to higher parts; the py- 
ramidal tracts to the cerebrum, and the cerebellar tract to 
the cerebellum. There are other tracts, which appear to 
terminate in groups of cells that act as relays between the 
fibers of the cord and the white matter of the brain. 

The bulb is pyramidal in shape, with the base above. 
It is related to the cord below and to the pons above. It is 
about one inch long, nearly one inch wide, and three fourths 
of an inch thick. Its surface shows fissures and columns; 
each half consists of an anterior pyramidal body, olivary, rest- 
iform body, and posterior pyramid (Fig. 68). The bulb has 
on its ventral surface the anterior median fissure continuous 
with that of the cord. The two bundles of white matter on 
each side of the anterior fissure are the anterior pyramids, 
and are separated from a round elevation, known as the oli- 




120 



THE BRAIN. 



IX, X 



vary body (Fig. 68). These pyramids are formed of fibers 
from the cord, some of the fibers being continuous below with 
those of the cord which form the direct pyramidal tract, but 
most being derived from the lateral column of the cord of the 
opposite side, known as the crossed pyramidal tract. The 
crossing of the lateral pyramidal fibers seen in the interior 
fissure is spoken of as the decussation of the 'pyramids. 

The two strands of fibers which make up the anterior 

pyramids degenerate down- 
ward when lesions or inju- 
ries of the cortex occur in the 
region known as the motor 
area. From this we know 
these fibers are efferent, or 
motor. In their course they 
are continuous through the 
crusta, or inferior part of 
the crura, with fibers in the 
internal capsule that pass to 
the region of the cerebrum, 
called the motor area (Fig. 
78). 

Lying between the olivary 
body and the posterior fis- 

Fig. 68. -Side View of Medulla. sure of the bulb is a band 
1. Orus cerebri. 2. Pons. 3. Pyramids. „ ni . . n „ 

4. Olivary body. 6. Lateral fissure. 7. 01 fibers Consisting 01 aiier- 
Posterior lateral fissure. 8. Restiform ° 

body. 9. Arm of Pons. 10. Connecting ent, Or Sensory, fibers from 
arm. 11. The fillet. Roman numerals re- J 7 

as r numbered pective pair ° f cranial nerves the posterior columns of the 

cord, and some of which, 
those forming the direct cerebral, enter the inferior peduncles 
of the cerebrum, and are known as the restiform body. 

The strand of fibers which come up from the posterior 
median column of the cord, appearing below the restiform 
body, are called the posterior pyramid of the funiadus gra- 
cilis. The strand near by from the posterior external column 
forms the funiculus cuneatus. Both of these strands ter- 
minate within the medulla, in the masses of gray matter. 




THE MEDULLA OBLONGATA. 



121 



called the nucleus gracilis and the nucleus cuneatus, respect- 
ively. From these nuclei, fibers pass across the central gray 
matter to parts of the brain above, their crossing being known 
as the upper, or sensory decussation. 

As we have stated, the cavity within the bulb is the 
fourth ventricle, and is formed by the widening of the central 
canal into the space formed by the divergence of the pos- 
terior pyramids, or funicule, which forms its lateral bound- 
aries in its lower half. The 
superior peduncles of the 
cerebrum, which pass down- 
ward and outward, form the 
lateral boundaries of its 
upper half. The pointed 
lower portion of the lozenge- 
shaped cavity thus formed 
is called, from its resem- 
blance to a writing pen, the 
calamus scriptorius (Fig. 
69). 

The upper angle of the 
ventricle reaches up to the 
level of the pons, and com- 
municates by the aqueduct 
of Sylvius with the third 
ventricle (Fig. 64). Its 




Fig. 69. — Posterior View of Medulla. 

1. Connecting arm of Pons. 2. Locus 

coeruleus. 3. Arm of Pons. 4. Funiculus 

roof IS formed m the upper teres. 5. Striae acusticas. 6. Trigorium 

Jri hypoglos. 7. Tubercule cuneatus. 8. 

rmrt bv n thin lovpr nf Clava. 9. Funiculus cuneatus. 10. Fu- 

pan U\ a mm layer 01 niculus gracilis . u . Posterior fissure. 12. 

tvhirp mnttpr cttrpalrprl witVi Apex. 13. Calamus scriptorius. 14. Fourih 
-Willie maiiei SireaKea Wlin ven tricle (band of). 15. Ala cinerea. 1G. 
gray, called the valve of Area acustic*. 17. Fovea superior. 

Vieussens, in the lower half by the reflection of the pia 
mater from the cerebrum. The posterior surface of the 
bulb and pons form the floor of the fourth ventricle. The 
white fibers, which emerge from the slight fissure in the 
floor, are known as the auditory striae, but we are in doubt as 
to how far they are connected with the auditory nerve. A 
number of small elevations on the floor correspond to the 



122 THE BRAIN. 

nuclei of gray matter, from which arise several cranial 
nerves. The olivary bodies and the two small detached 
masses, called the accessory olivary nuclei, furnish additional 
gray matter to the bulb. Gray matter traversed by longitudi- 
nal and transverse fibers forms the greater part of the central 
and lateral parts of the bulb, and on account of this struc- 
ture this portion is called the reticular formation. 

Functions of the Bulb. — From what has been said, we 
may now appreciate the importance of the bulb. We might 
judge from its complex structure that it has a varied function, 
which is true. It acts (1) as a conductor from the cord to the 
brain; (2) as a collection of nerve centers, both automatic 
and reflex ; ( 3 ) as means for the decussation of the fibers and 
the transition of the gray matter from the interior of the 
cord to the exterior of the brain (cortex) ; (4) as a source of 
most of the cranial nerves, being placed as it is, so that all the 
impulses passing between the spinal cord and the brain must 
pass through the bulb. For the greater part, the afferent im- 
pulses pass along the anterior pyramids where the decussa- 
tion {anterior pyramidal decussation) occurs of those fibers 
from the cord that have not already crossed in the cord ; i. e., 
of the crossed pyramidal tract. The fibers of the pyramidal 
tract are believed to decussate at various levels in the cord by 
the anterior commissure. The path of the sensory, or efferent, 
impulses is not completely made out, but it is probably, for 
the most part, along the posterior pyramids by way of the 
fibers which terminate in the nucleus gracilis and nucleus 
cuneatus of the bulb. From these nuclei, fibers pass around 
the front of the bulb to the opposite side in the strand, called 
the superior pyramidal decussation (sensory decussation). 
Some of the fibers are thought to decussate in the pons, and it 
is well established that the decussation of the fibers connecting 
the spinal cord and the brain is complete in the crura cerebri, 
so that all impressions to and from the hemispheres of the 
brain pass across the middle lines; injury to either hemi- 
sphere affects the sensation and motion of the opposite side 
of the body. 

The importance of the bulb as a nerve center is shown 



NERVE CENTERS. 123 

by the fatal results when it is injured or seriously diseased. 
Hanging is effective as a mode of putting criminals to death 
because the sudden displacement of the upper cervical verte- 
brae by the sudden drop of the body, when the trap is sprung, 
so injures the cord and its connection as to produce instant 
death. The piercing of a needle point in the center of the 
bulb produces instant death; and, on account of its control 
over the vital organs, the bulb is called the vital knot. It 
has been shown by experiment on the lower animals that the 
whole brain, with the exception of the bulb, may be grad- 
ually removed and the animal still live for some time; and 
it has been shown that the spinal cord may be removed up 
to the origin of the phrenic, a nerve arising from the third 
and fourth cervical nerve and sending fibers to the dia- 
phragm, without producing death for some time. 

NERVE CENTERS. 

Nerve centers, as to their action, may be grouped into 
the following classes: (1) automatic centers, (2) reflex cen- 
ters, (3) control centers, (1) tonic centers, and (5) psychic 
centers. 

Automatic centers are those which do not depend upon 
sensory impulses for the discharge of their motor impulses, 
as the rhythmic action of the heart and the respiration ; while 
they do not depend upon sensory impulses, the most active 
automatic centers are those which have close connection 
with sensory fibers. The most active automatic nerve cen- 
ters are in the brain. They also exist, as we have already 
seen, in the cord. 

Reflex Centers, are those in which a sensory impulse is 
essential to the discharge of nervous impulse of motion 
( afferent impulses ) . 

Control Centers, are those whose influence may be directed 
to controlling the action of subsidiary centers. The more 
important are the respiratory, vasomotor, *and sweat centers. 
Psychic centers are those in which consciousness and the 
will have control over the afferent impulses. The more im- 
portant centers of the bulb are : — 



124 THE BRAIN. 

1. The Respiratory Center. — This is bilateral, and is sit- 
uated behind the origin of the vagus nerve on each side of 
the posterior part of the calamus scriptorius. The branches 
of the vagus distributed to the lungs are efferent nerves, and 
they appear to be stimulated according to the condition 
of the blood as regards the proportions of the oxygen and 
the carbon dioxide. The impulse reaching the bulbular cen- 
ter is reflected along the efferent, or motor, fibers of the 
phrenic, intercostal, and other nerves associated with the 
respiratory movements. This center is also, automatic in 
its action, and the venous blood circulating in the bulb- 
ular center itself may excite it and lead to its automatic 
action. 

2. Cardiac Center. — This is also located in the bulb, 
one part of which gives origin to fibers whose stimulation 
accelerates the action of the heart through the sympathetic ; 
another part of which gives origin to fibers whose stimula- 
tion inhibits the action of the heart through the vagus. 

3. The Vasomotor {Vasoconstrictor) Center. — This is 
situated in the floor of the bulb a little above the calamus 
scriptorius. The center is bilateral, and controls the nerve 
supply to the unstriped muscles of the arteries, intestines, 
etc. Under ordinary conditions it keeps the arteries in a 
state of tonic contraction. Stimulation of the center leads 
to contraction of the walls of the arteries and a general rise 
of blood pressure ; inhibition of the center leads to dilation of 
the arteries and a fall of the blood pressure. This center con- 
trols subordinate centers in the cord. 

4. Center of Mastication. — This is believed to be sit- 
uated in the bulb, the afferent fibers being the sensory 
branches of the fifth and the tenth pairs of cranial nerves, 
and the efferent, the motor branches of fifth and twelfth 
cranial nerves. 

5. Center for Salivary Secretion. — This is also located 
in the bulb. 

6. Other Centers. — In the medulla there are also cen- 
ters for deglutition, vomiting, and coughing. 



REFLEX CENTERS. 



125 



Reflex Centers of the Cord. — The chief reflex centers of 
the cord are : — 

1. Muscular Tonic Center. — By means of this the spinal 
cord has an influence over the muscular system which keeps 
the muscles of the body in a continual state of slight con- 




Yin 



Fig. 74. — Superficial Origin of Cranial Nerves. 
The Roman numerals refer to the respective pairs of nerves. 

traction, which is called muscular tone. If the brain be 
injured or removed, the muscles still retain their tone; but 
if the cord be injured or diseased, the muscles lose their tone, 
and become flabby and loose. If the sciatic nerve of one leg 
of a frog be sectioned, the muscles of that limb become 
relaxed. 

2. Defecation Center. — This center is located in the 



126 THE BRAIN. 

lumbar region of the cord. It sends impulses which control 
the regular and tonic contraction of the sphincter muscle of 
the rectum. This center is also under the control of the 
brain, so that its action may be inhibited or augmented. 
This gives us the very important principle that constipa- 
tion may result from nervous affection. 

3. Micturition Center. — This center is also located in 
the lumbar region of the cord, and acts in a similar man- 
ner to that of defecation. It is stimulated to action by 
the presence of urine in the bladder or by impulses from 
the brain, producing the relaxation of the sphincter urethra 
and the expulsion of its contents. 

Other Centers. — There are also fibers which leave the 
cord by the anterior roots and join the sympathetic that 
control the secretion of the sweat. There are centers subor- 
dinate to those of the bulb which influence vasomotor action 
and the heart's action. 

The Cranial or Cerebral Nerves. — By the cranial nerves 
is meant those which have their origin either directly or 
indirectly within the cranium. They consist of twelve pairs. 
They are mixed in their function, some of special sense, 
some of general sensation, and others of motion. 

Their origin may be spoken of as superficial or deep. 
Their superficial origin extends from the frontal lobe of the 
cerebrum to the lower end of the bulb (Fig. 74). 

We can trace their fibers, however, into the substance 
of the brain to some special nucleus of gray matter, which 
is their real or deep origin (Fig. 75). With but one ex- 
ception, that of the olfactory, or first pair, the fibers go 
from the nuclei of origin and cross within the cranium. 
They are thus functionally connected with the cerebral cor- 
tex of the opposite side. The ultimate distribution of all 
except the tenth (pneumo gastric) and eleventh (spinal ac- 
cessory) is to some part of the head. 

Their names as to the order in which they pass through 
the dura mater of the base of the cranuim and their dis- 
tribution or function are : — 



THE CKANIAL JEEVES. 



pair. 


ORIGIN. 


DISTRIBUTION. 


FUNCTION. 


1. Olfactory. 


Olfactory bulb. 


S c hneiderian 
membrane of nose. 


Smell. 


2, Optic. 


Optic thalamus, 
corpus quadri- 
geminum, and cor- 
pus geniculata. 
cortex of occipital 
lobe. 


Retina. 


Sight. 


3. Motor ocull. 


Floor of the aque- 
duct of Sylvius. 


All the muscles of 
the eye, except 
rectus externus, 
obliquus supe- 
rior, and orbicu- 
laris palpebrarum. 


Motion, 


4. Pathetlcus. 
(Trochlcaris.) 


Floor of the aque- 
duct of Sylvius, 
below the third 
nerve. 


To obliquus supe- 
rior muscle of eye. 


Motion. 


5. Trifacial. 
(Trigeminus.) 


Floor of the 
fourth ventricle. 


Muscles of masti- 
cation, skin, and 
teeth. 


Sensation, m o - 
tion. 


6. Abducens. 


Fourth ventricle. 


External rectus 
of eye." 


Motion. 


7. Facial. 
(Portio dura.) 


Fourth lentricle. 


Face, ear, palate, 
tongue, and paro- 
tid and submaxil- 
lary gland. 


Motion, secretion. 


8. Auditory. 
(Portio mollis.) 


Fourth ventricle, 
and restiform 
body. 


Vestabular branch 
to vestibule of in- 
ternal ear ; coch- 
lear branch to 
cochlea of inter- 
nal ear. 


Hearing. 


9. Glosso-phar- 
yngeal. 


Fourth ventricle. 


Tongue, middle 
ear, tonsils, phar- 
ynx, and cover- 
ings of the palate. 


Sensation and 
motion. 


10. Pneumo gas- 
tric. 

(Par vagum.) 


Fourth ventricle. 


To pharynx, lar- 
ynx, esophagus, 
heart, great arter- 
ies, lungs, stom- 
a c h , intestines, 
liver, and spleen. 


Sensation and 
motion. 


11. Spinal acces- 
sory. 


Fourth ventricle 
and anterior cor- 
nu, as low as fifth 
and sixth. 


Sterno-mastoid 
and trapezius. 


Motion. 


12. Hypoglossal. 


Fourth ventricle. 


Hypoglossus and 
hyoid muscles. 


Motion. 



127 



128 THE BRAIN. 

The First, or Olfactory, Nerves. — These arise from a 
triple root in the under part of the frontal lobe, the olfac- 
tory lobes (Fig. 74). They are in reality lobes of the brain. 
They lie in a furrow on each side of the median fissure of the 
cerebrum. On reaching the cribriform plate of the ethmoid 
bone, they expand into bulbs, from the under surface of which 
ten or twelve fibers pass through the cribriform plate to be 
distributed to the mucous membrane of the nose, the end 
organ of smell. As we have noticed, their fibers do not cross, 
so that sensation received by this nerve does not go to the 
opposite side of the brain, as it does in the case of the other 
nerves. 

The Second, or Optic, Nerves. — These have their origin 
in the anterior corpora quadrigemina, the geniculate bodies, 
and the hinder part of the optic thalami. From this center 
they pass by what are called the optic tracts to form the optic 
commissure, where there is a partial decussation (Fig. 62) 
of the fibers ; from the commissure they pass to the eyeball, 
where they expand to form the retina. There are also fibers 
connecting their nuclei with the visual center of the cortex 
of the olfactory lobe. 

The fibers from the inner or nasal half of each retina 
decussate and pass backward to the opposite half of the brain, 
but the fibers from the outer, or temporal, half of the retina 
do not cross. 

The right optic tract, therefore, contains fibers from the 
outer half of the right retina, and the inner half of the 
left retina. The visual impression made by light from an 
object on the left side of the body is transmitted to the right 
side of the brain. The cutting of one optic nerve produces 
blindness in the corresponding eye, but a section of one optic 
tract produces half blindness of each retina (hemianopia). 

The Third, or Motor Oculi. — This pair arises in three 
distinct bands of fibers from the gray matter surrounding 
the aqueduct of Sylvius, near the median line ventral to 
the canal. The nucleus of origin extends to the back part 
of the third ventricle as far as the level of the anterior 



THE CRANIAL NERVES. 129 

corpus quadrigeininum. The fibers pass from their origin 
through the red nucleus to their superficial origin in front 
of the pons at the median side of each cms. The nerves 
of the sides decussate. They pass by the two branches 
to the orbits of the eye, where they are distributed (1) to 
the lifting muscles (levators) of the eyelids, (2) to the 
superior rectus, (3) inferior rectus, (4) internal rectus 
muscles. What movements of the eye are produced by this 
nerve ? There are also fibers which pass to the circular 
muscles of the iris, and to the ciliary muscle, to regulate the 
contraction of the pupil and the accommodation of the crys- 
talline lens. 

The Fourth, or Trochlears (Patheticus) . — This nerve 
arises from a nucleus situated below the aqueduct of Syl- 
vius, and extends from the back part of the nucleus of 
the third nerve to the hind level of the posterior corpus 
quadrigeminum. The fibers from each side pass round the 
central gray matter, and, on reaching the valve of Yieussens, 
they decussate in the median line, and appear at the front 
of the pons at the lateral edge of the cms. This nerve, like 
the third, is purely motor in its function, and is distributed 
to the superior oblique muscle of the eye. 

The Fifth, or Trigeminus. — In its mode of origin the 
fifth nerve resembles the spinal nerve in that it has a large 
sensory root with a ganglion (the Gasserian ganglion) and a 
smaller motor root to join the third branch which comes from 
it. The nucleus of this nerve is in the floor of the fourth ven- 
tricle. The fibers of the sensory root can be traced down the 
bulb to the upper part of the cord. The nerve appears 
in its superficial origin at the ventral surface of the pons 
near its front edge, at some distance from the median line. 

In function, the first and second divisions of the nerve 
which arise entirely from the large root are sensory, being 
distributed to the face, the teeth, the mucous membrane of 
the nose and mouth, and to the conjunctiva of the eye. 
The motor fibers pass to the muscles of mastication, the 
tensor tympani, and tensor palati. 
9 



130 



THE BRAIN. 



The Sixth, or Abducens. — This arises from a compact 
oval nucleus situated somewhat deeply at the back part of 
the pons, near the middle of the floor of the fourth ventricle 




Fia. 75. — Deep Origin of Cranial Nerves. 

Roman numerals refer to the superficial origin of the corresponding pair 
of nerves; i. e., IV to the fourth pair, and so on; the Arabic numerals to tneir 
deep origin, the pair indicated by the number. For the names of the unnum- 
bered parts, see Figs. 61, 62, and 63. 

(Fig. 75). It has connection with the nuclei of the third, 
fourth, and seventh nerves. It is nearer the median line 
than the nuclei of the fifth and seventh. It reaches the 



THE CRANIAL NERVES. 131 

surface at the posterior portion of the pons opposite the an- 
terior portion of the anterior pyramids. In its function it is 
entirely motor, and supplies only the rectus exicnius. 

The Seventh, or Facial (Portio Dura) . — This arises from 
the floor of the central part of the fourth ventricle hehind and 
in line with the motor nucleus of the fifth to the outside, 
and deeper down than the nucleus of the sixth. It emerges 
from the pons lateral to the sixth opposite the front edge 
of the groove between the olivary and the restiform body. 
It probably has connection with the hypoglossal nucleus. It 
is mixed in its function, and supplies (1) the muscles of 
facial expression; and its paralysis or injury on one side 
leads to a blank look on that side, with a dropping of the 
angle of the mouth and a loss of control of the muscle. (2) 
It sends branches to the submaxillary and parotid glands; 
it is thus a secretory nerve. (3) Through one of the branches 
{chorda tijmpani) it has some control over the sense of taste. 

The Eighth, or Auditory. — This arises from two nuclei, 
median and lateral, in the floor of the fourth ventricle, in 
the anterior part of the bulb in front and to the side of the 
twelfth nerve. It also has an accessory nucleus situated on 
the ventral surface of the restiform body. The nerve leaves 
the surface of the brain from the ventral surface of the 
fore part of the restiform body at the rear margin of the 
pons in two roots, the dorsal and the ventral. 

Most of the fibers of the dorsal root (cochlear) end in 
the accessory nucleus, but have connection with the median 
nucleus. Most of the fibers of the ventral root (vestibular) 
end in the lateral nucleus. This is the nerve of hearing. 
The cochlear branch is the auditory nerve proper, and the 
vestibular is distributed to the semi-circular canals, utricle 
and saccule, parts of the internal ear not directly concerned 
with hearing. 

The Ninth, or Glossopharyngeal. — As this nerve is so 
closely connected with the tenth and eleventh, we shall 
consider them together. They are considered as divisions 
of the eighth pair. The nuclei of the ninth and the 



132 THE BRAIN, 

eleventh seem to be combined, and appear to consist of two 
parts, one median, or common, origin, and three lateral 
origins: (1) the nucleus (nucleus ambiguus) which lies on 
the lateral side of the reticular formation of the origin of the 
vagus; (2) the one (fasciculus solitarius) situated in the 
bulb, ventral and a little lateral to the combined nucleus, 
glossopharyngeal nucleus; (3) the spinal portion which takes 
origin from a group of cells in the extreme lateral margin 
of the anterior cornu, spinal accessory nucleus. The com- 
bined nucleus reaches from the middle of the floor of the 
fourth ventricle down to the cord as low as the origin of 
the sixth or seventh cervical nerves. 

Its principal distributions are to the posterior and lateral 
walls of the upper part of the pharynx, the Eustachian 
tube, the arches of the palate, the tonsils, and the tongue. 

It is mixed in its function. It sends (1) motor fibers 
to muscles of the palate, pharynx, and tongue, (2) sensory 
fibers to the parts which it supplies, (3) a nerve of the spe- 
cial sense of taste from its fibers from the fifth. 

The Tenth, or Pneumogastric, or Par Vagum. — Its deep 
origin is as described for the ninth. Its superficial origin 
is by eight or ten filaments from the groove between the resti- 
form and the olivary body below the glossopharyngeal. It 
is the most widely distributed of the cranial nerves ; the more 
important points of its distribution are: (1) to a large por- 
tion of the mucous membrane of the under surface of the epi- 
glottis, the glottis, and the greater part of the larynx and the 
cricothyroid muscle; (2) to the mucous membrane and mus- 
cle fibers of the trachea, lower part of the pharynx, and to all 
the muscles of the larynx; (3) to the mucous membrane and 
muscular coats of the esophagus; (4) to the heart and great 
arteries; (5) by the pulmonary plexus to the lungs; (6) to 
the stomach and intestines, and by its terminal branches to 
the kidneys; (7) and to the liver and spleen. 

Throughout its whole course it contains both sensory and 
motor fibers. We cannot here fully consider the varied func- 
tion of the pneumogastric nerve, as it can be better learned 



THE CEREBELLUM. 133 

when considering the organs to which it is distributed. The 
more important functions are: (1) motor stimulus to the 
pharynx, esophagus, stomach, and intestines, to the larynx, 
trachea, bronchi, and lungs; (2) sensory; and (3) impart 
vasomotor influence to the same region; (4) inhibitory influ- 
ence to the heart; and (5) also inhibitory to vasomotor 
centers; (6) excitosecretory influence to the salivary glands; 
(7) motor stimulus in coughing, vomiting, etc. 

The Eleventh, or Spinal Accessory. — This arises by two 
distinct organs, one from a center of the floor of the fourth 
ventricle in connection with the common nucleus mentioned 
above, the other from the side of the anterior cornu of the 
spinal cord as low down as the fifth or sixth cervical 
nerve. The fibers from the two origins come together at 
the jugular foramen, but separate into two branches, the 
inner of which arising from the medulla, joins the vagus 
(pneumogastric), to which it gives motor fibers, while the 
outer gives fibers to the trapezius and sternomastoid muscle. 

The Twelfth, or Hypoglossal. — This arises from a very long 
nucleus in the bulb near the middle of the floor of the 
fourth ventricle, and extends back to the level of the olivary 
bodies. Its superficial origin is from a groove between the 
anterior pyramid and olivary body. Its fibers are distributed 
to the muscles of the hyoid bone and to the tongue. Its func- 
tion is purely motor. 

The Cerebellum. — Like the cerebrum, the cerebellum, 
or little brain, consists of two lateral hemispheres united by 
a central portion, called the vermiform process, situated 
beneath the medulla (Fig. 61). The cerebellum is situated 
in the posterior part of the cranium, beneath the cerebrum, 
and back of the medulla. It is separated from the cere- 
brum by a fold of the dura mater, called the tentorium. 

It connects with the brain by three pairs of fibrous stalks, 
called peduncles, or crura (Fig. 62). They are known 
as the inferior, or lower, the middle, and the superior 
peduncles. The restiform bodies become prolonged from 
the medulla to form the inferior peduncles. From each of 



134 THE BRAIN. 

the hemispheres of the cerebellum the middle peduncles 
pass to form the transverse fibers of the Pons Varolii. The 
peduncles which connect the cerebellum with the cerebrum 
are the superior. They form the upper part of the lateral 
boundary of the fourth ventricle, and are connected by the 
valve of Vieussens, which is a continuation of the white 
center of the vermiform process, and which forms the 
anterior roof of the anterior part of the fourth ventricle. 

The surface of the cerebellum presents quite a contrast 
with that of the cerebrum, the cerebellum being thrown in 
transverse furrows instead of convolutions. Like the cere- 
brum, it is composed of white and gray matter. The gray 
matter is on the exterior, forming its cortex. There is also 
a gray nucleus found near the center of each hemisphere, 
called the corpus dentatum. The white matter branches 
from the white center like a tree, forming what is called the 
arbor vitse. 

In its histological structure, the gray matter of the cere- 
bellum presents, (a) an outer layer beneath the pia mater, 
composed of delicate fibers with small nerve cells and large 
neuroglia cells; (6) an inner, or granular, layer next to the 
white center, the layer being composed of closely packed 
granule cells; (c) a middle layer made of a single layer of 
large pear-shaped cells (the corpuscles of Purkinje) (Fig. 
77), one thousandth to one eight-hundredth inch in diameter. 
Passing from the base of each of the cells, an axis-cylinder 
process goes to form one of the medullated fibers of the 
white matter, while from the opposite pole of the cell sev- 
eral processes pass outward into the outer layer. (Pig- 77.) 

Function of the Cerebellum. — While the evidence from 
experiments seems to be somewhat conflicting, and causes 
doubt upon certain points, the burden of evidence is in 
favor of the following : — 

1. That the function of the cerebellum is to secure the 
proper co-ordination of muscular movements, so that in 
such movements as standing, walking, talking, etc., the dif- 
ferent muscles employed may each act at the right moment 




,^y 



PLATE V. 



Fig. 43.— Muscles of Arm. 
1 Latissimus dorsi. 2 Coraco-brachi- 
alis. 3. Triceps. 4. Intermuscular 
septum. 5. Brachial is. 6. Radiales. 7. 
Tendon of biceps. 8. Biceps. 9. Long 
head of biceps. 10. Short head of 
biceps. 11. Cut portion of pectoralis 
major. 



Fig. 44.— Muscles op Arm and 
Forearm. 
1. Coraco-brachialis. 2. Cut end of 
flexor. 3. Cut end of pronator teres. 
4. Median nerve. 5. Flexor sublimis 
digitorum. 6. Flexor carpi ulnaris. 7. 
Tendon of flexor carpi radialis. 8. 
Flexor longis pollicis. 9. Cut end of 
pronator teres. 10. Supinator. 11. Su- 
pinator longus. 12. Cut tendon of the 
biceps. 13. Brachialis. 14. Deltoid. 



FUNCTION OF CEREBELLUM. 135 

with due force. Other parts of the cerebrospinal system 
have a part in the work of co-ordination, especially the 
spinal cord. The efferent impulses from the various parts 
of the body stream into the nerve centers during muscular 
activity, and to harmonize and control these various im- 
pulses so that locomotion will be effected or some definite 
movement produced is the work of co-ordination, and may 
be effected by the reflex centers, but they are largely under 
the control of the cerebellum. The afferent impulses are 
of several kinds: (1) From muscular sense, (2) visual sensa- 
tion, (3) the peculiar impulses that arise in the ampullary 
ends of the semicircular canals. These sensations do not 
always come into distinct consciousness. These various im- 
pulses may reach the cerebellum by one or the other of 
the peduncles, and may contribute to the regular association 
and action of muscular groups (see 2 and 3 below). 

The evidences upon which we base the above conclusions 
are: (1) That the removal or injury of the cerebellum pro- 
duces for some time, at least, a want of co-ordination; (2) 
that injury to one side causes inclination to fall toward the 
opposite side through failure of muscular power on the 
injured side; (3) that excitation of one side of the cere- 
bellum gives rise to muscular contraction of the same side; 
(4) that dissection and degeneration show that the connec- 
tion of the cerebellum hemisphere with the cerebral hemi- 
sphere is crossed; (5) that disease of the cerebellum very 
often leads to a staggering gait, with loss of muscular tone 
and power; (6) its removal does not affect the mental fac- 
ulties. 

2. It, at least in part, controls the power and tone of 
the muscles. 

3. It has no share in the higher intellectual functions. 
The Pons Varolii. — This lies above the medulla and 

between the hemispheres of the cerebrum, on transverse 
and longitudinal fibers intermingled with some gray mat- 
ter. The transverse fibers are both deep and superficial, 
arising from the middle peduncles of the cerebrum. The 



136 THE BRAIN. 

longitudinal fibers are arranged in bundles that pass down 
to the anterior pyramids of the medulla, where they decus- 
sate to form the motor tracts of the cord. There are other 
longitudinal fibers from the medulla and gray matter on 
the floor of the fourth ventricle which go to form the nuclei 
of the seventh, the sixth, and the fifth nerve. The motor 
fibers from the internal capsule to the facial nuclei decussate 
in the pons. This explains why an injury in the upper part 
of the pons affects the facial muscles of the opposite side, 
while injury in the lower part, after decussation occurs, par- 
alyzes the muscles of the same side. The motor fibers that 
go to the limbs decussate in the medulla. 

The Crura Cerebri (Fig. 62) . — Arising from the upper 
border of the pons, they diverge and pass into the cerebral 
hemispheres. By section, each crus is found to consist of 
two parts separated by a dark gray substance, called sub- 
stantia nigra. The anterior, or lower, part is called the 
'pes, or crusta, and consists almost entirely of longitudinal 
fibers, which are continuous above with some in the internal 
capsule, and below with some in the pons that go to the 
anterior pyramids of the medulla. The dorsal, or upper 
part, of the crus is called the tegmentum, and consists of 
gray matter and fibers continuous with part of the pons 
and medulla, called the formatio reticularis, which is sep- 
arated by transverse arched fibers and some gray matter. 
For the most part these fibers pass into the optic thalamus. 

Corpora Quadrigemina. — These are four rounded prom- 
inences placed in pairs over the aqueduct of Sylvius and 
above the pons and crura. They are chiefly composed of 
gray matter with white fibers externally and a few inter- 
nally. The white band which passes from the outer side of 
each of these prominences is called the arm, or brachium, 
and continues outward and forward. The bands from the 
posterior pair are lost beneath two prominences (the inter- 
nal geniculate bodies) near the posterior part of the optic 
thalami (Fig. 66). 

The bands from the upper pair pass into the bodies 



OPTIC THALAMI. 137 

known as the external geniculate bodies and the optic tract. 
The superior qnadrigemina are only connected histologically 
with the optic tract, but they are related to them function- 
ally as well, as is shown by their injury or destruction pro- 
ducing blindness. They appear to contain centers which 
have control over the contraction of the iris and over accom- 
modation. 

Optic Thalami. — These two masses are of oval shape, 
and project above into the lateral ventricles of the brain, 
their under surface resting on the tegmentum of the cms. 
The posterior and inner end of the thalamus projects over 
the arms of the corpora quadrigemina, and is known as the 
pulvinar (Fig. 66). Their inner sides form the lateral 
boundaries of the third ventricle. A- prolongation -of the 
tegmental part of the crura cerebri unite at their inner 
surface. On their outer side is the white matter of the in- 
ternal capsule formed by fibers from the crusta of the crura 
that pass into the cerebral hemispheres without entering the 
optic thalami. 

The optic thalami are composed of gray matter, with 
numerous nerve cells and white fibers which are mostly on 
the surface. They have connection with the posterior, or 
sensory, paths of the spinal cord through the tegmentum 
of the crura, and from their outer parts fibers pass onward 
to the cerebral hemispheres. 

The Corpora Striata. — They are two in number, and 
each consists of two parts: (1) a pear-shaped part, the cau- 
date nucleus projecting into the lateral ventricle of the 
same side in front of the optic thalamus, and (2) the part 
imbedded in the white substance of the cerebral hemispheres, 
called the lenticular nucleus. In a deep section of the brain 
between the two parts are seen the white fibers outside 
the internal capsule. The band of white fibers outside of 
the lenticular nucleus are those of the external capsule, and 
beyond the capsule is a thin lamina of gray matter, called 
the claustrum, which lies next to a lobe of the cerebrum in 
the fissure of Sylvius, called the central lobe, or island of Red. 



138 THE BRAIN. 

Each corpus striatum is made up of diverging white fibers 
mixed with gray matter, and in section it presents a striped 
appearance on account of its structure. 

The Internal Capsule. — This broad band of white fibers 
lies between the lenticular nucleus of the corpus striatum 
on the outer side and the inner caudate nucleus and optic 
thalamus on the inner side. The fan-like expansion of its 
fibers into the hemisphere is called the corona radiata. For 
the most part the fibers of the internal capsule connect the 
cortex of the brain with the crusta and bulb below. In 
horizontal section the internal capsule shows a bend called 
the knee, or genu; the part in front of the genu is called 
the front limb, and the posterior part, the hind limb. The 
fibers of the capsule curve away in many directions to 
various parts of the cerebral surface. 

In the internal capsule are found : — 

1. The Fibers of the Pyramidal Tract which can be 
traced from their origin in the motor areas of the cerebral 
cortex, around the fissure of Kolando, through the middle 
third of the internal capsule into the crusta of the cms 
cerebri, thence to the pons and the anterior pyramids of the 
medulla. Most of the fibers decussate at the lower part of 
the medulla as they pass into the spinal cord, where they 
form the crossed pyramidal tracts. Some of the fibers of 
this tract, however, pass to nuclei of the cranial motor nerves 
in the pons and medulla. The uncrossed fibers form the 
direct pyramidal tract. 

2. The fronto-cortical fibers which originate in the 
frontal convolutions anterior to the motor area, and pass 
down in the anterior third of the capsule through the crusta 
into the pons, where they appear to terminate in the gray 
matter. 

3. The temporo-occipital fibers which take origin 
in the temporal and occipital regions of the cortex, and pass- 
ing through the posterior third of the capsule, terminate in 
the outer part of the pons. 

In addition to the above-mentioned tracts, the internal 



THE CEREBRUM. 139 

capsule contains fibers from the nucleus caudatus of the 
corpus striatum that terminate in the pons, and also fibers 
from various parts of the cortex that terminate in the gray 
matter of the optic thalami. There seems to be little doubt 
that the pyramidal tract of the internal capsule is concerned 
in conveying voluntary motor impulses from the cerebral 
cortex to the muscles. 

The tract seems to be well marked, as is shown by the 
degeneration process, and is one of descending degeneration, 
having its trophic center in the cells of the gray matter of 
the cortex. As the fibers decussate, their injury produces 
paralysis of the muscles of the opposite side of the body 
and face. ,A paralysis of but one side is called hemiplegia. 
The posterior part of the hind limb of the internal capsule 
contains numerous sensory fibers connected with the oppo- 
site side of the body, and for this reason distribution of 
the internal capsule, produces a loss of both motion and sen- 
sation. 

Cerebrum. — By the cerebrum is meant the two large 
oval masses of gray and white matter that overlap all the 
rest of the brain. The term cerebrum usually includes 
all of the brain in front of the cerebellum and pons, includ- 
ing not only the cerebral hemispheres, the corpora striata, 
and optic thalami, but the corpora quadrigemina and the 
crura cerebri as well. As we have seen, these two masses 
are separated by the great longitudinal fissure (median) 
(Fig. 63), except at about the middle of half of their extent, 
where they are united at the depth of about an inch by the 
transverse fibers of the corpus callosum (Figs. 61 and 65). 
The surface of each hemisphere is very uneven, being thrown 
into numerous folds, called convolutions, or gyri, separated 
by depressions, called sulci. This folding tends to increase 
the superficial area, and increases the amount of the gray 
matter. The deeper depression or grooves are called fissures, 
and divide the surface of each hemisphere into iive parts, 
called lobes, while others separate the convolutions of each 
lobe from one another. 



140 THE BRAIN. 

The more important fissures are : The fissure of Rolando 
(Fig. 83), which begins near the middle of the longitudinal 
fissure at the top {vertex), and passes on the outer surface of 
each hemisphere obliquely downward and forward toward the 
great fissure of Sylvius ; the fissure of Sylvius, which begins 
on the under surface of the hemisphere, and passes upward 
and backward for two thirds of the distance from before 
backward; a long fissure (calloso-marginal fissure), begin- 
ning below on the inner part of the longitudinal fissure 
(mesial surface) and running backward for some distance 
above the corpus callosum and ending behind the fissure of 
Rolando. 

The more important lobes are the frontal lobe, which lies 
in front of the fissure of Rolando and above the fissure of 
Sylvius. By smaller fissures it is divided into four main 
convolutions, the superior, middle, inferior, and the ascend- 
ing frontal convolution (Fig. 76) ; the parietal lobe, which 
is bounded in front by the fissure of Rolando and below by 
part of the fissure of Sylvius. Its divisions are ascending 
parietal convolution situated around the end of the fissure 
of Sylvius and the angular convolution around the end ©f 
the temporal fissure ; the temporo-sphenoidal lobe, which lies 
below the horizontal part of the fissure of Sylvius, and pre- 
sents three parallel convolutions, called the first, or superior 
temporal, second, or middle temporal, and third, or inferior 
temporal. The occipital lobe, which is of small size, lies at 
the posterior end of the cerebrum, separated from the parietal 
lobe by the perpendicular parieto-occipital fissure. It has 
three convolutions, a superior, a middle, and an inferior. 
The central lobe, or island of Reil, concealed within the 
fissure of Sylvius, and may be seen by pulling apart the 
edges of the fissure. The gyrus marginalis lies between 
the surface of the hemisphere and the calloso-marginal 
fissure. The gyrus fornicatus lies between the calloso- 
marginal fissure and the corpus callosum. The gyrus unci- 
natus is located at the end of the temporo-sphenoidal lobe. 
The gyrus hippocampi, which is formed from the pos- 



STRUCTURE OF CEREBRUM. 



141 



terior end of the gyrus fornicatus, passes downward 
forward. The quadrate lobes are situated at the pos- 
terior end of 



marginal 



t h e 
convolu- 
tion and pari- 
etooccipital fis- 
sure, and just 
beneath this 
lobe lies the 
cuneate lobe. 

Structure of 
the Cerebrum.— 
From our dis- 
sections we 
have found it to 
consist of white 
and gray mat- 
ter ; the white 
being mostly in 
the middle of 
the hemisphere 
and extending 
into the convo- 
lutions, while 
the gray forms 
the outer part, 
or cortex, mak- 
ing a layer 
from one-sixth 
to one-fourth 
inch deep. 



2< 




Fig. 77.— Principal Constituent of Cortex of 

the Brain. 
1. Stratum zonale tangential fiber. 2. Small pyram- 
idal cells. 3. The white band strias. 4. The large 
pyramidal cell layer. 5. The layer of small irregular 
cells. 6. Lower limiting fibrous layer. 7. Large pyram- 
idal, with three long dendrites and spiny branches; 
the dendrites forming the fibrous layer above. 8. A 
small pyramidal cell. 9. Irregular cell, sending den- 
drites to lower limiting layer. 10. Small cells whose 
axis-cylinders go to make the outer layer. 11. Cell with 
many- branched axis-cylinders. 12. Fusiform cells of 
the banded layer, 
late cells. 



13. The far-reaching fibers, 14. Stel- 

The white matter consists of medullated nerve fibers arranged 
in bundles and supported by neuroglia. These fibers vary 
in size in different parts of the brain, but for the most part 
are smaller. The gray matter of the convoluted surface is 
arranged in a continuous layer, but divided into strata by 



XilEJ DJ\aU> 



light lines. The appearance to the naked eye of a section of 
the gray matter of the convolutions is shown in Fig. 66. It 
consists of a thin coating of white matter, best developed on 
the convolutions within the great median fissure; a layer of 
gray or reddish-gray matter ; a thin, whitish layer : a yellow- 
ish-gray stratum, sometimes showing a thin, whitish line; 
and the central white matter of the convolutions. 

The microscopic structure of the gray matter (Fig. 77) is 
complex, and presents five layers : (1) a superficial layer, with 
a few small ganglionic cells and an abundance of neuroglia ; 
(2) a layer of small pyramidal cells ; (3) a thick layer of py- 
ramidal cells, each having a process passing upward toward 
the surface from the pointed apex process, passing off later- 
ally, and a process from the center of the base, which becomes 
continuous with axis-cylinder of a nerve fiber. The pyram- 
idal cells become larger in the lower part of the layer, and 
bundles of nerves are seen passing downward from this layer 
into white matter ; (4) a layer of granules and small, irregu- 
lar nerve cells ; ( 5 ) a layer of fusiform cells running for the 
greater part parallel to the surface. The relation of the dif- 
ferent layers varies in the different regions of the brain. In 
the motor area the large pyramidal cells are well developed ; 
in the occipital region the granular is best developed ; while 
the pyramidal cells are few in the Sylvian fissure, the fusi- 
form cells are best developed of any part of the body. 

The axis-cylinder process of the pyramidal cells passes 
into the medullary center, to form either associated fibers 
connecting other parts of the same side, or commissural fibers 
through the corpus callosum, to the opposite hemisphere or 
projecting fibers, to the corpus striatum or optic thalamus, 
or by way of the internal capsule to the crura, pons, medulla, 
and spinal cord. 

Functions of the Cerebrum. — Our present knowledge of 
the functions of the cerebrum has been derived from various 
sources, the more important of which are: (1) the develop- 
ment of the cerebrum in the different races of men, — in the 
more intelligent the cerebrum is larger and more deeply con- 



FUNCTIONS OF THE CEREBRUM. 143 

voluted ; (2 ) from the comparison of the cerebrum of different 
vertebrate animals, it is observed that as animals increase 
in intelligence, the cerebrum increases in size, and the depth 
and number of its convolutions, and in its size in proportion 
to other parts of the brain and weight of the body of the ani- 
mal; (3) its imperfect development in idiots and imbecile 
persons; (4) the effect of injury of all or part of the cere- 
brum by disease or violence, producing loss of certain powers 
of the mind and body, or entirely destroying consciousness; 
(5) by removal, producing entire loss of intelligence, as 
shoAvn by experiments on the lower animals. 

If the cerebral hemispheres be removed from a frog, while 
still able to perforin many complex movements when prop- 
erly stimulated, it has lost all power of spontaneous move- 
ment. It can sit in a natural position, breathing quietly; 
but if undisturbed, remains motionless for an indefinite time. 
If placed on a board, and the board be lifted, it will crawl 
up to a position of equilibrium; if pinched, it will jump 
away, avoiding any obstacle in its way; if placed in water, 
it will swim until an object is put before it to rest on. It 
manifests no hunger, makes no effort to secure food, and 
shows no sign of fear. How different these reflex movements 
from those of the frog with its entire brain intact. The ani- 
mal seems to be a mere machine. 

If a pigeon be deprived of its cerebral hemispheres, it 
behaves very much in the same way. Undisturbed, it re- 
mains still, though by the proper stimulus it can be made to 
fly. It will starve to death on a heap of corn, though it begins 
to eat on holding its beak in it. It is, however, devoid of 
emotional and intelligent movements. 

On the higher animals but few observations have been 
made, as it is difficult to remove the cerebral hemisphere 
without producing fatal shock. A dog deprived of the 
cerebral hemispheres, as described by Goltz, after recovering 
from the shock of the surgical operation, walked and moved 
about in a normal manner, though often wandering restlessly. 
It slept at night, but any loud noise awoke it. A sudden 



light caused it to close its eyes, and an injury to one foot 
caused it to limp on three legs, showing that co-ordination 
Loth of simple and complex movements was not impaired. 

It at first would not eat, but had to he fed ; hut after some 
months it would help itself on being started. It seemed to 
be entirely wanting in the higher intellectual faculties. It- 
paid no notice to the barking of other dogs, or to the kind 
treatment of its master. While having the power of com- 
plicated movements, of taking food, and the sensation of 
taste and sight, it had no memory or other power that indi- 
cated intelligence. 

From these experiments, and clinical experience, it would 
seem that while the lower centers may receive afferent im- 
pulses, and give off efferent stimuli, resulting in complex 
movements, increasing in degree and importance as we pass 
from the spinal cord to the medulla and lower parts of the 
brain, the cerebrum alone has the power to convert afferent, 
or sensory, impulses into mental impressions that give rise 
to conscious perception and leave vestiges, which, as recol- 
lected ideas, form the basis of intellectual activity; and in 
the cortex alone can there issue those impulses known as vol- 
untary, or efforts of the will. We may therefore conclude 
that the cerebrum is ( 1 ) the seat of the mind ; its attribute, 
feeling, intellect, and the will; (2) that it exercises inhibitory 
or controlling power over the lower centers; (3) with its 
special areas to preside over the voluntary movements, those 
of speech, and as the centers of the special senses. 

If one of the cerebral hemispheres becomes injured, the 
power of mind may be carried on by the other hemisphere, 
but, as we have seen, there would be a complete paralysis of 
the parts of the body to which the nerves from the affected 
parts go. 

As we have found, there are certain reflex acts which are 
natural or inherent in the spinal cord. By the help of the 
brain, however, new systems of reflex paths may be set up in 
the nervous structures, and we may become possessed of many 
acquired or artificial reflex acts, — those actions which at first 



CEREBRAL LOCALIZATION. 145 

require close attention and continuous effort of tlie will 
become by repetition so ingrained in the nervous structure 
that a single sensation or a single impulse from the brain 
may set the whole train in action, and thus may be per- 
formed unconsciously. Thus many acts of attention and 
will become reflex. Our voluntary and reflex acts shade into 
each other, a series being often connected by one or both 
kinds. In a strictly voluntary act there must be the guidance 
of an idea, perception, and volition ; but in acts of habit, con- 
scious effort is not required beyond giving an impulse that 
starts a series. A habit has been defined as a reflex dis- 
charge from some nervous center, the most complex being, 
Professor James says, " nothing but connected discharges in 
the nerve centers due to the presence there of systems of 
reflex paths so organized as to wake each other up success- 
ively, the impression produced by one muscular contraction 
serving as a stimulus to provoke the next, until a final im- 
pression inhibits and closes the whole chain." 

Cerebral Localization. — It was formerly thought that the 
brain acted as a unit, and therefore injury to any part of the 
cerebrum would produce a loss of mind and instant death, 
but of late years we have come to look upon the brain as not 
only complex in structure, but localized in function; i. e., 
that the different parts of the cerebral cortex have different 
functions. There are a number of things which give support 
to this view, among the most important of which may be men- 
tioned: (1) The removal of the cerebrum of a living ani- 
mal, layer by layer, and carefully noting the effect; (2) 
stimulation by means of electricity of certain areas of the 
cerebrum, and noting the effect, that while one area stim- 
ulated the contraction of a certain set of muscles, another 
area would give rise to the contraction of an entirely dif- 
ferent set of muscles; (3) the effect of disease of different 
parts of the cerebrum in producing paralysis differing in 
degree and kind, some affecting vision, some affecting motion 
of the lower limbs, some affecting motion of the upper limbs ; 
(5) by the study of the degeneration of the nerve fibers; (6) 
from embrvological observation. 
10 



146 



THE BRAIN. 



The more important motor areas are situated in the con- 
volutions around the fissure of Kolando. They are: (1) The 
outer surface of the upper part is concerned with the move- 
ments of the leg; (2) the middle with the movements of the 
arm; (3) the lower part with the movements of the face and 
mouth, and on the inner surface of the median associated 
with the head, arm, trunk, and leg; (4) the speech area in 
the third frontal convolution, a lesion of which produces loss 
of power of speech, or motor aphasia, as it is called; (5) 
sensory area in the posterior part of the first temporal con- 
volution. The distribution of these various areas may be 
learned by a study of Fig. 78. 

It should be remembered that these areas are not distinct, 
but often overlap. These areas do not have the power of 
originating efferent impulse, but they must be first awakened 
by sensory impulses. Cerebral localization is of great aid to 
the physician in locating the seat of a disease of the cerebrum. 
The Sympathetic System. — The sympathetic system con- 
sists (1) of a double chain of ganglia and fibers extending 
from the cranium to the pelvis along each side of the vertebral 
column, and from which branches are distributed both to the 
cerebrospinal system and to other parts of the sympathetic 
system. With this chain may be included the small ganglia 
in connection with those branches of the fifth cerebral nerve, 
which are distributed in the region of the organs of special 
sense, as the ophthalmic, optic, sphenopalatine, and submax- 
illary ganglia; (2) various ganglia and plexuses of nerve 
fibers, which give off branches to the thoracic and abdominal 
viscera, the nerves to important plexuses of which are the car- 
diac, solar, and hypogastric (see Figs. 79 and 80). To the 
plexuses, fibers pass from the prevertebral chain of ganglia, 
also from the cerebrospinal nerves; (3) various ganglia, and 
plexuses in the substance of the viscera, as in the stom- 
ach, intestines, and urinary bladder. These are of small size, 
most of them being microscopic. They have free communi- 
cation with other parts of the sympathetic system, and also 
to some extent with the cerebrospinal; (4) by some the gan- 



SYMPATHETIC PLEXUSES. 



147 



glia on the posterior roots of the spinal nerves on the glosso- 
pharyngeal and vagns and the sensory root of the fifth cere- 
bral nerve (Gasserian ganglion) are considered as sympa- 
thetic nerve structures. 

From the researches of Gaskell 
we may classify the sympathetic 
ganglia into: (1) The main svm- 
pathetic chain, consisting of twen- 
ty-fonr pairs, extending from 
above downward, beginning in the 
cervical region in a single gan- 
glion and terminating below in a 
single ganglion, and constituting 
a connected chain lying upon the 
bodies of the vertebra?. This 
chain is called the lateral, or ver- 
tebral, ganglia; (2) a more or less 5 
distinct chain in front of the ver- 
tebra?, consisting of the semilunar 
inferior mesenteric and solar 
plexuses called the collateral gan- 
glia; (3) the ganglia which are 
situated in the organs and tissues 
themselves, called the terminal 
ganglia; (4) the ganglia of the 
posterior roots of the spinal cord. 
The connection of these vari- 
ous parts is as follows 
visceral branch 
munications (Fig. 57) of each ^ xu ° 8 f^ H ?JSStrif P S iS™ 
spinal nerve pass first into the 't^g^tiJ^At 
lateral chain, from which glia - 7 - Sacral ganglUl - 
branches (rami efferentes) pass into the collateral ganglia, 
and from these again are given off branches which go to the 
organs to end in terminal ganglia. In the thoracic regions 
the rami communicantes are composed of two parts, white 
and gray. The white can be traced backward into both spinal 




The Fig. 79.— Diagram of Trunk, 
Showing Principal Sym- 
or ramus, com- pathetic Plexuses. 



J. rl Jii IN Hil\ VUU5 fil b ± U.M. 




Fig. 80. — Solar and Hypogastric Plex- 
uses with Their Connections. 
1. Suprarenal capsule. 2. Hepatic artery. 
3. Superior mesenteric artery. 4. Renal 
artery. 5. Inferior mesenteric artery. 6. Sa- 
crovertebral angle. 7. Common iliac vein. 8. 
Common iliac artery. 9. Semilunar or coeliac 
ganglion. 10. Greater splanchnic nerve. 11. 
Lesser splanchnic nerve. 12. Renal ganglion. 
13. Superior mesenteric ganglion. 14. Branch 
to aortic plexus. 15. Gangliated cord of sym- 
pathetic. 16. Inferior mesenteric ganglion. 
17. Branch to aortic plexus. 18. Communi- 
cating branch. 19. Gangliated cord. 20. 
Phrenic ganglion. 9, 12, and 20 go to make up 
the solar plexus. 



nerve roots of their cor- 
nua, and in the other 
direction partly into the 
lateral sympathetic 
chain and partly into 
the great splanchnic 
nerves, and so into the 
collateral ganglia, with- 
out entering the lateral 
chain at all. The upper 
white branch (ramus), 
however, proceeds up- 
ward, and joins the su- 
perior cervical ganglia 
instead of passing 
downward into the 
splanchnics. There are 
other branches which go 
downward to the lum- 
bar and sacral plexuses. 
The gray branch 
(ramus) of all the 
spinal nerves is the only 
apparent representative 
of the visceral branches 
in the regions above the 
second thoracic nerve 
root and below the sec- 
ond lumbar nerve root, 
with the exception of 
the roots of the second 
and third sacral nerves, 
which also have white 
rami, and are made 
up of non-medullated 
fibers, and pass from 
the ganglia to be dis- 



SYMPATHETIC GANGLIA. 



149 



tributed chiefly to the spinal column, to the spinal mem- 
branes, and to the spinal nerve roots themselves. For this 
reason we may consider the white rami as the visceral 
branches proper. 

The fibers of the white medullated visceral nerves are 
distinguished by the fineness of their fibers, being about one 
fourth the diameter of ordinary medullated fibers (1.8 /a to 
2.7**, instead of 14.4 /a to 19/x). These white fibers are 
found principally in the spinal nerve roots of the thoracic 
regions, but they are also 
found in the second and 
third sacral nerves, form- 
ing the nervi erigentes, 
which pass directly to the 
hypogastric plexuses, 
from which branches pass 
upward into the inferior 
mesenteric ganglia, and 
downward to the bladder, 
rectum, and generative 
organs. These differ from 
the visceral branches of 
the thoracic region in that 
they do not communicate 
with the lateral ganglia. 

The efferent nerve 
fibers of the sympathetic 
system supply (1) the 
muscles of the vascular system, and in their function are 
vasoconstrictor and cardiac augmentor, vasodilator, and car- 
diac inhibitor; (2) visceral muscles, giving to them both 
vasomotor and vasoinhibitor fibers; (3) the secretory gland 
cells. These will be considered more at length when we study 
the organs to which they are distributed. 

Ganglia, Their Structure and Function. — The sympathetic 
ganglia consist of the nerve fibers traversing them ; the nerve 
fibers which originate in them ; and the nerve or gan- 




Fig. 81.— Section of Pneumogastric 
Nerve, Human. (Highly magnified.) 

1. Sheath of nerve (epineurium). 2. 
A fasciculus of nerve fibers. 3. Sheath of 
fasciculus (perineurium). 4. Nerve fibers. 
What appears to be cells with nuclei are 
the cut end of the nerve fibers; the outer 
ring being the nerve fiber sheath (neuri- 
lemma), the lighter space the medullary 
sheath, and what appears to be the nucleus, 
the axis-cylinder. (Brinckley, C. W. B.) 



XHlii lNILLiVUUO OlOXH/M. 



glion corpuscle, which gives origin to the fibers and other 
corpuscles that appear free. In the sympathetic ganglia of 
some of the nerves, cells of a very 
complicated structure are found. 

The chief functions of the main 
sympathetic ganglia are, (1) to effect 
the conversion of medullated into non- 
medullated fibers ; 
(2) to give a nutri- 
tive influence (tro- 
phic) over the 
nerves which pass 
from them to the 
periphery ; ( 3 ) to 
increase the num- 
ber of fibers at the 
same time that 
they cause the re- 
moval of the me- 
dulla. It was for- 
merly thought that 
ganglia possessed 
the power of reflex 
action similar to 
that of the spinal 
cord, but this is 
now considered 
doubtful. 

The Structure of 
Nervous Tissue. — 
It is composed of 
the white and the 
gray matter. The 
gray matter is found in the cortex of the brain, in masses, 
in the substance of the white matter of the brain, in the ven- 
tricles, and in certain bodies at the base of the brain, in the 
interior of the spinal cord, and in the ganglia. 



Fig. 82 A — Medul- 
lated Nerve Fiber 
(blackened by osmic 
acid). 

Black central por- 
tion axis-cylinder. 
Schwann's sheath or 
neurilemma. The 
cell-like body (nerve 
corpuscle) lies be- 
tween the neurilem- 
ma and the second 
coat of the nerve 
(white substance of 
Schwann, medullary 
sheath or myelin). 




Fig. 82 B.— Non-medul- 
lated Fiber (Kemak's 
fiber). 

Fiber from vagus of dog. 
b. Fibrils, n. Nucleus, p. 
Protoplasm surrounding 
it. 



STRUCTURE OF THE NERVES. 151 

The white matter is found on the interior part of the 
brain, connecting the various gray masses on the exterior 
part of the spinal cord and in the nerves. The fibers of the 
white matter are bound into large or smaller thread-like 
masses, called nerves, which bring into relation the nerve 
centers with the rest of the body. The larger nerves are 
somewhat complex in structure. The sheath which invests 
the nerve is called the epineurium, the part which surrounds 
the bundles (funiculi) which make up the nerve is called 
perineurium (Fig. 81), and the membrane which passes be- 
tween the fibers of the bundle (funiculus), the endoncurium. 

The separate threads which compose the nerve are called 
fibers. They vary greatly in size ; the largest are found in 
the spinal nerves, and are from 14.4/m to 19/x in diameter. 
There are nerves mixed with these which measure only 1.8/* 
to 3.6/a. These small fibers are found principally in the vis- 
ceral nerves; they pass to sympathetic ganglia, where they 
leave as non-medullated fibers, and are distributed to the 
involuntary muscles. 

When fresh, the nerve fiber appears very simple, but on 
standing, or by means of special reagents, it is shown to be 
complex. The nerve fibers may be classed into two varieties : 
the medullated, or white, and the non-medullated fibers 
(fibers of Remak). The medullated fibers (Fig. 82 A) con- 
sist of a central core, the continuation of the process from a 
nerve cell, and the essential part of the nerve, called the axis- 
cylinder, which is gray and granular ; outside this is a sheath 
of white color, fatty in nature, which stains black with osmic 
acid, known as the medullary sheath of white substance of 
Schwann; and investing the medullary sheath, is a thin 
homogeneous membrane of elastic nature, called the prim- 
itive sheath, or neurilemma. The medullary sheath is con- 
stricted at somewhat regular intervals, known as the nodes 
of Ranvier, and the intervening space between the nodes 
as the internode. The axis-cylinder is not simple, as it 
appears at first, but it is made of exceedingly small fibers, 
which stain readily with gold chloride. 



The non-medullated fibers (Fig. 82B) have no medullary 
portion or white substance of Schwann, and do not present, 
therefore, the double contour of the medullated fibers; they 
are unaffected by osmic acid. 

The covering of the axis-cylinder is a nucleated, fibril- 
lated sheath. * These fibers branch frequently. The medul- 
lated fibers are found in the white matter and in the nerves 
having their origin in the brain and spinal cord, the non- 
**z,<&*~~-*<L.* medullated in the sym- 

pathetic system, but a 
few are found in the 
spinal nerves, mixed 
with the medullated 
fibers. 

How Nerves End. — - 
This will be considered 
under the respective 
tissues to which they 
are distributed. 

Structure of Gray 
Matter. — The struc- 
ture of the gray matter 
differs greatly in the 
parts of the 

1. Dendron. 2. Nucleus. 3. Neuroglia. 5. , ,i 

Body of cells. 7. Nucleolus. 6. Dendrites, nervous System, the 
(Brinckley, O. W. B.) n , , . -,.„., 

cells having diner ent 
form, shape, and structure as they become specialized in 
their function. As a rule, nerve cells have large, round 
nuclei, in which are one or more nucleoli. The protoplasm 
of the cell is granular, but may be striated or reticulated. 
Some contain a yellowish-brown pigment. Some nerve cells 
are small, generally spherical or ovoid, and regular in out- 
line, and inclosed in a nucleated sheath. These are found 
principally in the sympathetic ganglia. There are other 
cells which are large, caudate or stellate (Fig. 83), and hav- 
ing one, two, or more processes (poles), and are called uni- 
polar, bipolar, or multipolar, according to the number of 
poles they have. 




Fia. 83. 



Nerve Cells from Spinal Cord 

of Calf. various 



THE NEURON. 



153 



These processes often divide and subdivide, breaking up 
in some cases into a fine arborescence. The processes appear 
tubular, and filled with the same kind of granular material 
as the cell. If we are to take the conclusion of recent inves- 
tigation, these do not anastomose, as was formerly thought, 
but end, as stated before, 
in fine arborescence, which 
interlace, but do not join. 
There is, therefore, no con- 
tinuous chain between cell 
and cell (Fig. 84). 

Old authors speak of 
the nervous system being 
made up of two distinct 
substances, the white mat- 
ter (nerve fibers) and the 
gray matter (nerve cells). 
Better histological methods 
have enabled us to deter- 
mine nearer the true nature 
of the nervous system, and 
the modern view is that it 
is composed of one element, 
called the neuron (Figs. 84 
and 85), or nerve unit, 
which is imbedded in and 
supported by a substance 
called neuroglia. The 
neuron consists of a cell 
body, a number of branching processes, called dendrites, and 
a long process, neuraxis, which becomes the nerve fiber. A 
nerve center is simply an aggregation of neurons arranged 
in different ways in the different parts of the nervous system. 

It was discovered by Golgi that the individual nerve fiber 
of the central nervous system gives off in its course branches, 
which pass off from it at right angles for a short distance, 
and then turn back and run in various directions. These 




Fig. 84.— The Olfactory Bulb. 
(Diagram of structure.) 

1. Nasal epithelium. 2. Glomerulus of 
olfactory bulb. 3. Mitral cells. 4. Cen- 
tral fibers. 



branches are called collaterals, which end in fine, brush- 
like bodies, called brushes, or in little bulbous swellings, 
which come in close contact with some nerve cell. The col- 
laterals are more numerous in nerve centers. 

Neuroglia It was formerly thought that neuroglia 1 was 

a form of connective tissue, inasmuch as it performs func- 
tions similar to that of connective tissue, but its origin ex- 
cludes this idea, as it is derived from the epiblast, the same 
embryonic layer from which the nervous system is derived. 
The tissue is made up of numerous cells, from which are 
given off numerous branches, some of which may again branch 
to form a fine network. The arrangement and form of the 
neuroglia cell differ in different parts of the nervous system, 
according to the arrangement of the nervous structures it 
supports. 

HYGIENE OF THE NERVOUS SYSTEM. 

Need of Exercise. — The nerves, like the muscles, need 
exercise. It is a biological law that the proper exercise of 
an organ results in its development and strength, while its 
disuse brings loss of power and degeneration (atrophy). 
Would we have strong nerves, a vigorous and active brain, 
we must give them constant and judicious exercise. Spas- 
modic efforts will not secure this; as with the muscles best 
results are only secured by persistent and regular exercise. 

The increased power and size of the various parts of the 
nervous system is due to the same cause as in the muscles, a 
better supply of pure blood, giving a greater store of fresh 
material for the discharge of energy, and more effective 
removal of the waste products. This gives the system great 
power for its general function, and also a large reserve force 
to overcome disease, and to meet any extra demands that 
may be made upon it. 

^Velocity of Nervous Impulse.— The velocity of nerve impulse is influenced by 
various conditions, some of the more important of which are the following: (1) 
Cold lessens its velocity, and also temperature, 25° C. ; (2) electricity, anelectro- 
tonus lessens, while cathelectrotonus increases; (3) the length of the nerve; (4) 
nature and strength of the stimulus. 

The average velocity in the frog is 27 meters, and in man it has been esti- 
mated from 30 to 60 meters per second. 



HYGIENE OF THE NERVOUS SYSTEM. 155 

Fatigue of Nerve Cells. — There is a limit to the power 
and activity of the cells of the various centers and parts of 
the nervous system. If the exercise or stimulation is too 
prolonged, exhaustion of the cells may result, and to every 
cell there is a limit of its power of restoration after exercise. 
In extreme fatigue it is the nerve cells and not the muscles 
which succumb to exhaustion. 

Under influence of stimuli, the nerve cells become 
shrunken and irregular in outline, while the nuclei of the 
cell and of the inclosing cell wall become smaller. These 
regain their normal size and shape after proper rest, or after 
refreshing sleep. There is marked difference in the appear- 
ance and size of the nerve cells as we awaken in the morning, 
refreshed by the night's sleep, and as we retire in the evening, 
fatigued by the heavy labors of the day. These differences 
in the condition of the cells may be readily noticed by exam- 
ination with a microscope. 

Sleep. — While we do not fully understand the mystery of 
sleep, yet experiment and our experiences show us its need 
and importance. The respiration and circulation become 
slower, the activities of the body lessened, the constant storm 
of afferent sensation that has been battering at the nerve 
centers, and great nervous stimuli which they call forth, cease 
to a large degree. The nervous activities are restricted to 
the reflex centers, and in very profound sleep to the automatic 
centers, thus relieving the cerebrum and the higher centers. 
Sleep is nature's restorative. 

The higher the organism and the greater the development 
of the nervous system, the greater the need of sleep. 

The Amount of Sleep.— It takes some time for the cells to 
regain their normal condition and size after they have been 
subjected to several hours of activity. Our sleep, in order to 
be refreshing, must be uninterrupted for several hours. 
There will be a very close relation between the activity of 
the individual and the amount of sleep that an individual 
takes. Great activity demands a corresponding amount of 
sleep. Most adults should take at least eight hours of sound 



156 



THE NERVOUS SYSTEM. 



sleep. Children require more than adults; the aged less. 
The amount required varies also with the habit and indi- 
vidual peculiarities. 

Sleeplessness. — Normally, the waste products which col- 
lect in the blood of the brain from the activity of the nerve 
cell give a sense of fatigue, which begets sleep; but their 

presence may 
excite cerebral 
activity and 
produce a 
sense of wake- 
fulness. Un- 
due blood ten- 
sion in the 
brain may 
produce a 
similar effect. 
Overwork o r 
undue excite- 
m e n t may 
bring about 
these condi- 
tions. If sleep- 
lessness (in- 
somnia) con- 

1. Nerve cell. 2. Neuraxon. 3. Dendron. 4, Dendrite. 5. tinues for 
Arborescence of dendrites. (The neuron is made up of 1, 2, . 

3, 4, and 5.) 6. Dendroa of another neuron, b, with its S O m e time, 
branches interweaving with those of a. (Brinckley.) , 

and repeats 
itself night after night, it should receive immediate attention. 
If due to overwork or overexcitement of the nerve centers, 
the cause should be removed. 

There are a number of medicines (hypnotics) that have 
the power of producing sleep, but these should not be given 
except under the direction of a physician. Sleep may often 
be produced by very simple means. The first thing is to 
relieve the mind of all care and excitement. The blood pres- 
sure of the brain must be lessened. The reclining position, 




Fig. 85. — Diagram of Neurons. 



NUTRITION OF THE NERVOUS SYSTEM. 157 

quiet and darkness, are favorable to sleep. A foot bath, rub- 
bing the lower limbs, a lunch of light digestible food, or a 
warm bath followed by vigorous rubbing, and gentle exer- 
cise, will reduce the blood tension of the brain by calling the 
blood to other parts of the body, thus bringing about sound 
sleep. 

Nutrition of the Nervous System. — While the nervous 
system regulates all motion, controls all vital process, yet 
it is dependent upon the very action which it itself excites. 
While the salivary gland cannot secrete without the proper 
nervous stimulus, the nerve center is dependent upon the 
proper action of the salivary gland for its proper growth; 
so is it with the other organs. Like the other organs of the 
body, the activity, strength, and development of the nerv- 
ous system depend upon pure blood to give it material for 
growth and discharge of nerve energy, and to carry away the 
waste products of its activities. 

Good blood is dependent upon a proper supply of oxygen 
and removal of the carbon dioxide, and this requires proper 
action of the respiratory organs. The food material must be 
prepared by the alimentary tract, and to get the most from 
our food it must be thoroughly digested. ~Not only must 
the blood be pure, and laden with energy-giving materials, 
but its flow must be regulated to secure the proper blood 
supply and pressure. This last condition is dependent upon 
the proper action of the heart and the blood vessels. How 
important it is that these processes be well performed ; that 
the nervous system, which is dependent upon them, be prop- 
erly nourished. 

Many of the so-called cases of nervous exhaustion (neu- 
rasthenia) are not really so much a disease (i. e., an actual 
degeneration or structural change in nervous matter) of the 
nerve tissues, as a lack of their proper nutrition, resulting 
from sluggish circulation, poor blood, and imperfect diges- 
tion. The remedv is to be sought in most cases not in sed- 
atives or stimulants, but in a change of habit, judicious exer- 
cise, proper food, and an improved digestion. 



158 THE NERVOUS SYSTEM. 

True nervous exhaustion is comparatively rare, and is a 
very serious condition, and demands the most skillful treat- 
ment. 

Habit. — The repetition of an act renders its performance 
easier. This is due to the fact that when afferent impulses 
and efferent stimuli have passed over a certain path, their 
course becomes fixed. Acts which required our attention 
become reflex; i. e., can be carried on without our attention. 
When the course of the action has thus become fixed, we call 
it a habit. Many of our acts, which would demand con- 
sciousness, become reflex, relieving the higher centers; as 
the cerebrum is relieved from the care of these movements, 
it is free to take charge of the higher, or intellectual, 
activities. In playing a difficult piece, the musician directs 
his attention to the interpretation of the melody, the har- 
mony, and expression of the piece, leaving to the reflex 
centers the mechanical execution, and through the training 
he has received, the fingers strike the right notes, in the right 
time, and with the right force, without his thought or atten- 
tion. Had his attention been required for the mechanical 
execution, what note to strike, how long, and with what force, 
the skillful rendering of the piece would have been impos- 
sible. Skill is thus possible, where otherwise our movements 
would be restricted to the simple ones. 

The law of habit applies as well to our moral being as to 
our physical. It has been said that character is a bundle of 
habits, and that we are what we make ourselves by our acts. 
If we engage in right acts until adult age, we will form 
habits of right doing, and our tendencies will be for the right ; 
if we engage in wrongdoing, bad habits will be formed, and 
our tendencies will be to the wrong. 

Kepeated acts of kindness, love, truthfulness, honesty, 
and industry in youth become habits, and the doing of them 
becomes a joy. It is just as true that continued acts of un- 
kindness, indolence, falsehood, and dishonesty produce habits 
that bring misery. 

If we would have noble characters, we must accustom our- 



EFFECTS OF ALCOHOL ON THE NERVOUS SYSTEM. 159 

selves to the doing of noble deeds, the thinking of noble 
thoughts, the loving of noble things. Habits, when once 
formed, are difficult to break, and often when persons who 
form bad habits desire to do right, they find themselves 
chained to evil by their habits. Good habits are equally 
as strong. Youth is the habit-forming period of life; what 
we are at twenty we are likely to be at forty. One of the 
strongest safeguards against evil is youth and manhood spent 
in right doing. Habits not only impress the individual, but 
as well his descendants, and may persist through several 
generations. 

Every organism is under the influence of heredity and 
environment. By the former we have certain temperaments, 
appetites, and tendencies, some of which impel to noble ac- 
tion, while others, if followed, tend to degrade us. 

The environment, if favorable, tends to the improvement 
of the organism, or if unfavorable, to its injury or destruc- 
tion. 

The effects of heredity may, to a large degree, be over- 
come by proper environments. We cannot prevent our 
hereditary tendencies and physical inclinations, but we may 
overcome them by putting ourselves under the influence of 
the best environments. Crime has a physiological as well as 
a moral basis. The scanty food, the unwholesome air, the 
poorly lighted apartment, the evil associations, have much 
to do with the production of crime. Alcoholism is not only a 
crime, but a disease as well. 

In no system of the body are these influences more marked 
than in the nervous system, and hence the importance of 
wholesome food, well-ventilated and well-lighted rooms, judi- 
cious exercises, cheerful and ennobling surroundings. 

Effects of Alcohol on the Nervous System. 1 — Evil as the 
effects of alcohol on the other systems of the body may be, 



i The action of alcohol on the nervous system depends on the dose, its size, 
and the frequency of its repetition. In a moderate dose, the whole nervous sys- 
tem is stimulated to a slight extent, probably directly, but chiefly by the serond- 
ary effect due to the vascular dilation and cardiac stimulation. In this stage 
the higher functions are most affected. If the dose be large, the stage of stimu- 



ICO THE NERVOUS SYSTEM. 

they are not to be compared in magnitude to the injury to 
the nervous system. Many of the injuries of the other organs 
of the body, due to the use of alcohol, are due in many cases 
to its effect on the nervous system. 

In moderate doses, alcohol x acts as a cerebral stimulant ; 
in large ones, a depressant. The former, if kept up, results 
in nervous exhaustion in proportion to their frequency and 
amount." The large dose may bring immediate unconscious- 
ness and depression, and if the dose is very large, immediate 
death. 

A person intoxicated is truly poisoned (as the word 
expresses). The abnormal pulse, flushed face, the respira- 
tion, the lower temperature, the staggering walk, or the uncon- 
sciousness, show this. Alcohol also affects the motor and sen- 
sory areas of the cerebrum, as well as the centers of co-ordina- 
tion, as is seen in the bewildered vision, the imperfect speech, 
and the staggering gait. It affects the automatic and reflex 
centers of the medulla, as shown in the flushed blood vessels, 
the quickened pulse and respiration. This affects the blood 
vessels of the brain, as well as the other parts of the body, 
and may result by continued use in chronic congestion, 
putting in danger the life of the person by sudden death 
from apoplexy. It also affects the metabolism and the nutri- 

lation soon passes into one of depression as before, the higher function being 
affected descending from the higher to lower centers, the lower being the last to 
yield to its depressing effects. The loss of the powers would be in the following 
order: judgment, imagination, control of the emotions, control of speech, con- 
trol of delicate muscular activity, as writing, the power to walk, reflex centers 
of the cord, as those of micturition, the respiratory centers, and lastly, the 
heart. It should be observed that the order of depression is the order of 
stimulation; i. e., the first to be stimulated is the first to be depressed; the one 
most easily stimulated, the one easiest depressed ; the one most difficult to stimu- 
late is the one last to be paralyzed. In moderate dose alcohol acts as a stimu- 
lant; in larger dose as hypnotic, or narcotic. 

i In action of alcohol, opium, chloral, and cocaine, we have two very impor- 
tant laws illustrated: 1. Drugs which affect functions progressively, affect, first, 
the higher function, and then the others in order of rank, the rank being 
determined by the order of development in the individual ; the intellectual being 
the last acquired are the first to be affected. Kespiration and circulation being 
the first acquired by the organism are the last to be affected. This is well 
illustrated in the action of alcohol. This is called the law of dissolution. 2. 
Those drugs which in moderate dose excite; in large dose depress and paralyze. 
Great care should be exercised in the use of alcohol in sickness, as by a large 
dose we may defeat the very purpose we seek by paralyzing, when we desire to 
stimulate. Large doses of alcohol do not stimulate the heart, but depress it. 

2 The effect of a given quantity of alcohol will depend very much on the 
individual. What to one would act as a stimulant might in another act as a 
narcotic. 



M» IZ <* EM CJ ' 




3D ~- 

O r.-r 
B» » « 
c. =?■ 



-3 




EFFECTS OF ALCOHOL ON THE NERVOUS SYSTEM. 161 

tion of the nerve cells, (1) by the poor quality of the blood, 
and (2) by its narcotic effect on the metabolism of the cell, 
which may result in the injury of the tissue, producing what 
is called " softening of the brain." 

Alcohol, when immoderately used, produces such a morbid 
craving for it that the person becomes, for the time being, 
entirely crazed in his craving for anything that will satisfy 
his consuming thirst, — a disease called dipsomania. 

Persistent and inordinate use of alcohol may produce 
the dreadful and dangerous disease known as delirium tre- 
mens. Both of these diseases are acute forms of alcoholism, 
and are affections of the nervous system. 

The effects do not stop here; these morbid conditions 
affect the health of the children of parents who are habitual 
users of alcohol, and even their children's children. 



11 



CHAPTER VI. 

THE SKELETAL SYSTEM. 
DEMONSTRATIONS AND EXPERIMENTS. 

I. Make a careful study of the skeleton (Tig. 86), and 
notice : — 

1. General arrangement of the bones. 

2. How they are joined to the central column of bone 
{vertebral column). 

3. The articulation of the arms at the shoulder, and the 
lower limbs at the hip bones. 

4. What use do you see for the collar bones ? 

5. How are the ribs attached ? 

6. How many curves has the spinal column? What 
reason can you give for these curves ? 

7. How is the head attached to the spinal column ? 

8. How many separate bones (vertebrae) go to make up 
the spinal column ? 

9. What parts have vertebrae? (See Fig. 97.) 

10. Is there any means of communication between the 
cavity of the skull and the canal of the spinal column (spinal 
canal) ? 

II. What organs are contained in the above-named cavi- 
ties ? 

12. If nerves are given off by the spinal cord, how can 
they get out of the spinal canal? How could blood vessels 
enter the spinal canal? 

13. Make a careful examination of the bones of the head. 

14. How many of the bones have movable joints ? Give 
reasons for the kinds of joints. What advantages are secured 
by the cranium being made of separate bones ? 

15. What use can you see for the numerous openings 
from the cranial cavity? 

16. What provisions do you note in the form and struc- 
ture of the orbit ? 

17. How does the size of the body of the vertebrae vary 
from above downward ? What advantage is secured by this ? 

18. How do the form and size of the spinous processes 
differ ? What advantage does this secure ? 

162 



DEMONSTRATIONS AND EXPERIMENTS. 163 

19. Notice the bones of the extremities. How are they 
adapted to their respective functions ? 

20. What provisions do you notice in the skeleton for the 
attachment of muscles ? 

21. Into how many classes can the bones be grouped as 
to their form ? 

22. From Fig. 86, also from Figs. 87 to 108, learn the 
names of the bones. 

23. Read the description in the text, and see how it agrees 
with your own observations. 

2-i. Notice the various joints of the body. 

25. Taking the elbow, the humerus at the shoulder, the 
vertebra?, and the bones of the cranium as types, into how 
many groups can you class the joints of the skeleton ? 

26. Determine what joints belong to the types given. 

27. Do you find joints which do not conform to the types 
given ? 

28. How does the knee joint differ from the elbow joint? 
Can you give a reason for the difference ? 

29. Compare the shoulder and hip joints. Give reasons 
for the difference. 

30. Examine the humerus. Notice its expanded ends 
(extremities) : the intervening portion (the shaft). What 
reasons can you give for the difference in the upper and lower 
extremities of the humerus ? 

31. Compare the humerus and the femur. Try to find 
reasons for the difference observed. 

32. Are the bones which make movable articulation ex- 
panded at the portion articulating? 

33. Make a longitudinal section of one of the long bones 
(Fig. 109) (a fresh bone). 

a. Note structure of the extremities. 

b. Note structure of the shaft. 

c. Why are the extremities spongy and the shaft compact 
and hollow ? 

d. Notice the membrane (periosteum) surrounding the 
bone. 

e. The lining (endosteum) of the cavity (medullary 
canal). 

f. The nature of the substance (marrow) contained in 
the canal of the shaft. Take a small amount of marrow 
from the medullary canal, tease and examine with both high 




Fig. 86. — The Skeleton. 
1. Cranium. 2. Inferior Maxillary. 3. Spinal Column. 4. Clavicle. 5. Hu- 
merus. 6. Ulna. 7. Carpal bones. 8. Metacarpal bones. 9. Phalanges. 10. Fe- 
mur. 11. Patella. 12. Fibula. 13. Tarsal bones. 14. Metatarsal. 15. Phalanges. 
16. Tibia. 17. Pelvis. 18. Radius. 19. Sternum. 20. Scapula. (Brinckley.) 



164 



Axial 



Head «{ 



Skull 



Ear 



I Face 



Chest 



L Spine 



£ 

9) 

W 1 



Shoulder 

Arm 
Forearm 



f Car- 



pus 



Hand 



Upper Row 



Lower Row 



3 
O 

G 
<U 
ft 
ft 



fHip 
Thigh 



Foot 



I L 



' Frontal 


1 


Parietal 


2 


Occipital 


1 


Temporal 


2 


Sphenoid 


1 


t Ethmoid 


1 


( Malleus 


2 


■j Incus 


2 


( Stapes 


2 


f Malar 


2 


Lachrymal 


2 


Nasal 


2 


, Vomer 


1 


Turbinated 


2 


Superior Maxillary 


2 


Palate 


2 


. Inferior Maxillary 


1 


( Ribs 


24 


■j Sternum 


1 


( Hyoid 


1 


f Cervical 
I Dorsal 


7 


12 


{ Lumbar 


5 


I Sacrum 


1 


I Coccyx 


1 


j Scapula 
1 Clavicle 


2 


2 


Humerus 


2 


j Radius 
{ Ulna 


2 


2 


f Scaphoid 


2 


1 Semilunar 


2 


J Cuneiform 


2 


[ Pisiform 


2 


f Trapezium 


2 


J Trapezoid 


2 


j Os magnum 
I Unciform 


2 


2 


j Metacarpal 
I Phalanges 


10 


28 


Os Innominatum 


2 


Femur 


2 


I Tibia 


2 


i Fibula 


2 


( Patella 


2 


Os Calcis 


2 


Astragalus 


2 


Cuboid 


2 


' Navicular 


2 


Internal Cuneiform 2 


Middle Cuneiform 


2 


External Cuneiform 2 


j Metatarsal 
I Phalanges 


10 


28 



165 



166 THE SKELETAL SYSTEM. 

and low power. Examine some of the marrow (red) from 
the spongy portion of the long bone. Compare structure 
with the marrow taken from the medullary canal. Deter- 
mine whether the marrow contains any oil by soaking 
two grams or thirty grains of marrow in eight or ten times 
its volume of benzine for forty-eight hours. Pour off the ben- 
zine solution, and let it evaporate from a beaker or evaporat- 
ing dish. Compare the weight of the oil obtained with the 
weight of the marrow taken. Express proportion in per 
cent. Burn twenty grams or three hundred grains of mar- 
row in a porcelain crucible, and determine the amount of 
ash. Express in per cent. Make a solution of the ash, and 
test for sodium potassium, calcium, and phosphates. (See 
General Test in Appendix. ) Does marrow contain proteids ? 
Determine the amount of water in the yellow marrow by 
thoroughly drying twenty grams at 120° C. How much 
has it lost in weight by drying? What per cent of the 
marrow is water ? 

g. Do you find any place on the bones for the entrance 
of blood vessels? 

34. Make a vertical section of a small piece of one of the 
fiat bones, and note its structure, as before. Take care to 
have piece of uniform thickness, and as thin as possible. 
(See Appendix.) Mount dry, making ring of Brunswick 
Black to hold cover. Examine with three-fourths or two- 
thirds objective; compare with Eigs. 22 and 23, and deter- 
mine name of parts. Examine with one-sixth objective. 
Make a longitudinal section in the same way. What is the 
direction of most of the Haversian canals (see Eig. 23) ? 

35. Take a fresh bone (the femur of a cat, dog, rabbit, 
or chicken), and soak for several hours in dilute acid (muri- 
atic, one part to ten parts of water). Eemove the bone from 
the solution, and wash it to remove the acid. Set the solution 
away, as you will need it again. What changes do you notice 
in the bone ? Dry, and weigh the bone. Boil the bone for 
several hours in several times its own volume of water, and 
then set away to cool. Test the gelatinous substance obtained 
for proteids. What does the test show in regard to the com- 
position of the bone ? Evaporate to dryness over a sand bath 
the liquid in which the bone soaked. After letting the 
powder cool, weigh it carefully. The powder you obtain is 
the mineral matter of the bone, that has dissolved in the 



DEMONSTRATIONS AND EXPERIMENTS. 167 

acid. How does its weight compare with the weight of 
the bone before it was treated with the acid ? How does the 
weight of the bone after being treated with acid and drying 
compare with the first weight of the bone? What part of 
the bone is animal matter ? What part mineral ? Dissolve the 
powder from the evaporation of the liquid in which the bone 
was soaked, in distilled water, test (see Appendix) for mag- 
nesium, calcium, potassium, and phosphates. 

Weigh a fresh bone, and then burn over a Bunsen flame 
on a piece of platinum foil, or in a porcelain crucible. If 
you do not have either of these, burn on a shovel over the 
coals in the stove. Weigh the ashes, and compare with the 
weight of the bone. How does this proportion compare with 
the proportion of mineral obtained in 35 ? Divide the ashes 
into three parts, and test (see Appendix) the first part for 
carbonates, the second for chlorides, and the third for phos- 
phates. How does your analysis agree with that given in 
the text ? 

THE JOINTS. 

1. Examine the knee joint of the rabbit, dissect out the 
bands (ligaments) which bind the bones. In how many ways 
do they run? Are they all alike in form? Determine by 
means of the microscope their structure. How do you 
account for the moist surface where the parts come in con- 
tact ? Make a section to show structure of the inner or smooth 
surface (synovial membrane). Make a longitudinal section 
of the head of the bones, and notice the cap of cartilage that 
tips the bones. Of what use is it to the joint ? How many 
kinds of ligaments do you find ? Examine in a similar man- 
ner the joint at the fore foot? Notice relation of the tendons 
and ligaments. How is the friction of the tendons pre- 
vented ? 

2. Dissect out one of the joints of the vertebral column. 
Notice the arrangement of the ligaments. How do you 
account for the cartilage (interarticular) between the ver- 
tebra ? 

3. Examine some of the grooves over which tendons 
move, as the lower part of the forearm. Examine the mem- 
brane of the smooth surface over which the tendons move. 
Is it like the membrane you found in the joints ? 



168 THE SKELETAL SYSTEM. 

4. Test the synovial fluid for proteids. Does it contain 
corpuscles ? Does it coagulate on standing ? 

THE SKELETON. TEXT. 

Use of Bones. — As we have seen, motion is necessary to 
the welfare of the body. The muscles would be almost use- 
less without firmer parts upon which to act. Again, many 
parts of the body are soft and delicate, and need support and 
protection. To serve these functions, we have the frame- 
work of the body, consisting of the firm, hard parts (bones), 
the softer and more elastic part (cartilage), found between 
the bones, and sometimes tipping the bones, and the band-like 
parts (ligaments) joining the bones together. 

The tendons, which attach the muscles to the bones, and 
the connective tissue which enters as a supporting tissue into 
every organ of the body, also belong to the framework of the 
body. 

In speaking of the skeleton, we generally have reference 
to the bones of the body, but the skeleton includes not only 
the bones, but the cartilage and ligaments which enter into 
the make-up of the joints, and when thus preserved, is known 
as a natural skeleton. But the skeleton is difficult to preserve 
in this condition, and the bones are generally put together 
by means of wire or bolts, or otherwise, and when thus put 
together, it is called an artificial skeleton. 

Divisions of the Skeleton. — The skeleton is composed of 
(1) the central column of small bones (vertebral column) 
and the head, which make up the axial skeleton, and (2) 
the pectoral girdle, the upper extremities, the pelvic girdle, 
and the bones of the lower extremities, which make up the 
appendicular skeleton. 

For convenience in study, the skeleton may be divided 
into the regions head, trunk, upper and lower extremities. 

The head is made up of twenty-eight bones, consisting of 
those of the cranium, the face, and the ear. 

Bones of the Cranium. — The bones of the cranium are 
eight in number. Each bone is composed of an external and 
an internal plate, with cellular bone (diploe) between them. 




Titt'-'CGO' 




?£.??>£. 



170 THE SKELETAL SYSTEM 

The bone in the fore part of the cranium is the frontal; it is 
convex on the outside and concave on the inside, its inner 
surface being marked for the convolution of the brain. The 
prominent ridge on its lower portion is the orbital process, 
which roofs the orbit of the eyes. Above the orbital ridge 
(Fig. 88) are two cavities (frontal sinus), which are lined 
with mucous membrane, and communicate with cavities in 
the ethmoid bone. It articulates above with the two parietal 
bones (Fig. 87), below with the sphenoid (Fig. 89), eth- 
moid, superior maxillary (Fig. 87), lachrymal, and malar, 
and in front with the nasal (Fig. 87). 

Parietal Bones. — The bones which form the side walls of 
the cranium are called the parietal bones. They are quadri- 
lateral in form, smooth on their outer surface, but internally 
marked for the convolutions of the cerebrum. The lower 
portion on the outside is overlapped by the squamous portion 
(Fig. 87) of the temporal bone. In front it articulates 
with the sphenoid and the frontal, above with the opposite 
parietal, below and laterally with the temporal, and behind 
with the occipital (Fig. 87). 

Occipital Bone. — The bone forming the back of the head 
is the occipital bone (Fig. 91). It also forms a part of the 
base of the cranium. It is round in form and the thickest 
of the cranial bones. The lower portion projects forward, 
forming what is called the basilar process, upon which rests 
the lower surface of the medulla oblongata. Just back of the 
basilar process is a large opening, called the foramen mag- 
num, through which passes the spinal cord. On each side of 
this foramen is a projection of bone, forming the occipital 
condyles, which articulates with depressions in the atlas. It 
articulates in front with the parietal and the temporal, and 
below with the body of the sphenoid. 

Temporal Bones. — At the side of and beneath the parietal 
bones, lie the temporal bones (Fig. 93). They are very irreg- 
ular in form, and composed of three portions, an upper, 
scale-like part overlapping the parietal, and called the squam- 
ous portion, from the lower border of which there projects 
the zygoma, which forms, with a portion of the malar bone, 



THE SKELETON. 171 

the zygomatic arch, to which are attached important muscles. 
At the base of this process is the cavity (Glenoid) with 
which . the condyle of the inferior maxillary articulates. 
Back of this is the opening into the middle ear (external 
meatus). 

Projecting forward and downward from this opening is 
a slender, rounded portion of bone, called the styloid process 
(Fig. 89), for the attachment of muscle going to the tongue 
and the hyoid bone. The rounded, conical-shaped projection 
back of this is called the mastoid process, for the attachment 
of the sterno-cleido mastoid muscle. It forms the greater 
part of the portion of the temporal bone, called the mastoid 
portion. It is very porous, and contains the mastoid cells, 
which are lined with mucous membrane, and have communi- 
cation with the ear. The part of the temporal bone below 
the zygoma and in front of the mastoid process, is called 
the petrous portion, from its hardness; in it is hollowed out 
the cavities of the middle and internal ears. The temporal 
bone articulates with the parietal above, behind with the 
occipital, in front with the malar, the inferior maxillary, and 
sphenoid. 

The Sphenoid Bone. — This bone is situated in the an- 
terior part of the base of the cranium, and articulates with 
all the other bones of the cranium and five of the face, bind- 
ing them firmly together, hence its name (the wedge bone). 
In form it resembles a bat with its wings spread. It artic- 
ulates with the basilar process of the occipital, and forms a 
part of the floor on which the brain rests. 

In the body of the sphenoid (Fig. 92) bone are two large, 
irregular cavities. These cavities are not found in children, 
but increase in size as age advances. Their thin walls aid 
much in the resonance of the voice. To the sphenoid are 
attached eleven muscles. 

The Ethmoid Bone. — This bone is a very light and spongy 
bone, cubical in form, located at the anterior part of the 
base of the cranium between the two orbits, and at the root 
of the nose and entering in the formation of the orbits and 
the nasal fossa. It articulates with fifteen bones: the sphe- 



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THE SKELETON. 173 

noicl, the frontal, the nasal, the superior maxillary, larchry- 
mal, palate, interior turbinated, and the vomer. There are 
no muscles attached to "the ethmoid. 

Bones of the Face. — There are fourteen bones in the 
face ; viz., the two nasal, two superior maxillary, two lachry- 
mal, two malar, two palate, two inferior turbinated, one 
vomer, and one inferior maxillary. 

The upper and lower jaws are the fundamental bones 
of mastication, the other bones of the face being acces- 
sory; the chief function of the bones of the face being to 
provide an apparatus for mastication, and having a second- 
ary function of providing for the sense organs (eye, nose, 
tongue), and a cavity for the respiratory and vocal organs. 
" Hence the variation in the shape of the face in man and 
the lower animals depends chiefly on the question of the char- 
acter of the food and their mode of obtaining it." 

The Nasal Bones. — These two bones are placed side by 
side, forming the bridge of the nose. They are small, 
oblong, and varying in size in different individuals. They 
articulate with four bones, the frontal and ethmoid, the op- 
posite nasal, and the superior maxillary. They receive a 
few fibers of the occipito-frontalis muscle. 

The Superior Maxillary Bones. — They (Fig. 94) are sit- 
uated beneath the nose and between the cheek bones. The 
superior maxilla presents for study a body somewhat cuboid 
in form, hollowed out in its interior to form a large cavity 
called the antrum of Highmore, and four processes: the 
malar, the portion articulating with the cheek bones; the 
nasal, forming part of the cavity of the nose; the palatal, 
the thin portion of bone forming the greater part of the roof 
of the mouth; and the alveolar, the portion of the bone in 
which the teeth are set. Excepting the lower jaw, it is the 
largest bone of the face, forming by its union with its fellow 
of the opposite, the whole of the upper jaw. It articulates 
with nine bones, the frontal, ethmoid, the nasal, vomer, 
malar, lachrymal, inferior turbinated, palate, and the oppo- 
site maxillary. 



174 THE SKELETAL SYSTEM. 

To it are attached twelve muscles, the more important 
of which are the orbicularis palpebrarum, masseter, buccin- 
ator, internal pterygoid, and orbicularis oris (Fig. 36). 

Not only is it of interest from the part it plays in 
mastication, but as well from a surgical point of view, from 
the various diseases to which its parts are liable. The 
antrum is lined with mucous membrane, and communicates 
with the nasal fossae ; the thin walls of this cavity add much 
to the resonance of the air passages. 

The Lachrymal Bones. — They (Fig. 88) are located in 
the fore part of the orbit, resembling in form, thickness, 
and size a finger nail. These two bones are the smallest and 
most fragile bones of the face. Each bone has one muscle 
attached to it, and has articulation with the frontal, ethmoid, 
superior maxillary, and inferior turbinated. 
K The Malar Bones. — These two small bones (Fig. 88), 
situated at the upper and outer part of the face, form the 
prominence of the cheek and part of the outer wall and 
floor of the orbit. They are quadrangular in form, and artic- 
ulate with the frontal, sphenoid, temporal, and the superior 
maxillary. Each malar bone forms attachment for five mus- 
cles, the more important of which are fibers from the tem- 
poral and masseter muscles. 

The Palate Bones. — They are (Fig. 94) situated at the 
back part ,of the nasal fossae, being wedged in between the 
superior maxillarv and one of the processes (pterygoid) of 
the sphenoid. They are somewhat L-shaped, and so placed 
that the short part of the L forms a part of the hard palate, 
and the longer portion forms a part of the nasal fossae. 
Each bone has six articulations, the sphenoid, - ethmoid, 
superior maxillary, inferior turbinated, vomer, and the oppo- 
site palate. Each forms attachment for four muscles. 

The Inferior Turbinated. — These scroll-shaped bones are 
situated one on each side of the outer wall of the nasal 
fossae. Each articulates with four bones, the ethmoid, su- 
perior maxillary, lachrymal, and palate. They have no 
muscles attached to them. 



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17 6 THE SKELETAL SYSTEM. 

The Vomer. — This is a single bone, and resembles a plow- 
share, varying very much in size and form in different indi- 
viduals. It articulates with six bones: the ethmoid and 
sphenoid of the cranium, and with the two superior maxil- 
lary, the two palate bones of the facej and with the cartilage 
of the septum of the bone. There are no muscles attached 
to the vomer. 

The Inferior Maxillary Bone. — It (Fig. 95) is situated 
beneath the superior maxillary, the upper portion by the 
posterior process {condyloid process), articulating with the 
glenoid fossae of the temporal bones. It is the largest and 
strongest bone of the face. It is made up of a curved 
horizontal portion which has the form of a horseshoe, the 
body and two perpendicular portions, the rami, which join 
with the body at nearly a right angle. The form varies 
very much with the age. 

On the horizontal portion is the alveolar process, in which 
are set the lower teeth. The inferior maxillary serves for 
the attachment of fifteen pairs of muscles, the more impor- 
tant of which are the buccinnator, masseter, orbicularis, di- 
gastric, temporal, and pterygoid. 

Hyoid Bone. — It is situated at the base of the tongue, 
to which it gives support and attachment. In general out- 
line it is U-shaped, and consists of a body and four proc- 
esses called cornua, two of which are large and two small. It 
articulates with no bones. 

It serves for the attachment of numerous muscles, espe- 
cially of the tongue, larynx, and pharynx. 

THE THORAX. 

This forms the protecting cage which contains the prin- 
cipal organs of respiration and circulation. It is conical 
in form, being narrow above and broad below, flattened 
from before backward, and longer behind than in front. On 
transverse section it is somewhat heart-shaped. Its posterior 
support is the dorsal vertebra?. Its bony walls consist of the 
ribs, costal cartilage, and the sternum. 



THE SKELETON. 1?? 

The Sternum. — This bone forms the line of support in 
front. It (Fig. 100) is a flat, narrow bone, made up in 
the adult of three pieces ; and from its fancied resemblance 
to an ancient sword, these have been called, (1) the manu- 
brium — the upper piece, or handle ; (2) the gladiolus — the 
middle piece, or blade; (3) the ensiform, or xiphoid appen- 
dix — the lower piece, or tip of the sword. 

It has numerous indentations for the reception of the 
costal cartilage. The upper part of the manubrium is curved 
to receive the clavicle. It articulates with the clavicles and 
seven pairs of costal cartilage. It serves for the attachment 
of nine pairs and one single muscle, the diaphragm. 

The Ribs. — These (Fig. 100) form the side bars of the 
thorax, and extend, with the exception of two pairs, from 
the costal cartilage in front of the vertebrae behind, with 
which they have articulation at two points : the facets of the 
body of the vertebrae and the transverse process. 

They are so placed, one below the other, that spaces are 
left between them, called intercostal spaces. The ribs con- 
sist of twelve pairs, seven of which are attached to the ster- 
num by the costal cartilages, and are called true ribs. The 
remaining five are called false ribs ; the first three pairs are 
attached by cartilage to the rib above ; of these the last two are 
free at their anterior extremity, and are called floating ribs. 

Typically, a rib consists of two extremities, a posterior 
or vertebral and an anterior or sternal, with an intervening 
portion, the body, or shaft. This is best seen in the ribs from 
the middle of the series. The posterior extremity consists 
of a head having a kidney-shaped articulating surface, and 
the neck, which is the flattened portion, and which extends 
outward from the head. On the neck there is an eminence, 
tubercle, where the rib articulates with the transverse proc- 
ess of the vertebrae. 

The shaft is thin and flat, and differently curved in the 
different ribs (see Fig. 100). While the ribs have the fea- 
tures mentioned in common, they differ very much in them- 
selves to adapt them to their special uses. 
12 



178 



THE SKELETAL SYSTEM. 



IK 



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The ribs have twenty pairs of muscles attached to them ; 
among the more important of these may be mentioned the 
internal and external intercostals, scaleni, and diaphragm, 
which are concerned in respiration. 

THE VERTEBRAL COLUMN. 

The spine, or vertebral column, forms the 
posterior and axial part of the skeleton. It 
is divided into three regions, the cervical, 
the dorsal, and the lumbar (Fig. 96). In 
man the spinal column has four curves: 
convex anteriorly in the cervical region, 
concave in the dorsal, convex in the lumbar, 
and concave in the pelvis. It is smaller 
above, and increases quite gradually to the 
sacrum. 

The separate bones are called vertebra; 
twenty-four of these are called true ver- 
tebra, and nine are called false (the sacrum 
five, and the coccyx three or four), as they 
are scarcely movable. 

Most of the vertebrae (Fig. 96) consist of 
a body, the anterior portion, from which 
there projects two thin layers which meet 
posteriorly, and from the neural arch, 
from which project seven processes — two 
pointing upward and two pointing down- 
i; - ward, the articular processes; two point- 

fig. 96. — Side mo' laterally, the transverse processes; and 

View or Spinal & t/7 r 

Column. one backward, the spinous process. In the 

1. Atlas. 2. Axis. , . 7 „ , r t i • 

3. The seventh cer- lower portion oi the pedicel is a groove 

vic&l vBrfccforfL 4 

First dorsal verte : over which the spinal nerves and the blood 

bra. 6. Twelfth r 

dorsal vertebra. 5. vessels pass. 
First lumbar. 7. x 

sacrum ^"oocc x Tlie P edicels Wltn tne lamina form a 

ring, the neural arch, and these placed one 
upon the other form the neural canal, in which is contained 
the spinal cord. Between each of the bodies of the vertebrae 
are pads of cartilage; the bodies are also rimmed with car^ 



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THE VERTEBRAL COLUMN. 



179 



tilage, thus adding much to the flexibility and elasticity of 
the vertebral column, and increasing the power of movement 
of the trunk of the body. The vertebrae are firmly bound 
together by ligaments, giving not only freedom of movement 
in bending, but great strength also. The separate vertebrae 
with the interarticular cartilages lessen very much the shocks 
on the brain which it would receive were it not for this pro- 
tection. 





Fig. 97. A.— A Vertebra, Side View. 
1. Body. 2. Pedicel. 3. Transverse 
process. 4. Superior articular process. 
5. Spinous process. 6. Inferior articu- 
lar process. 



Fig. 97. B.— A Vertebra, Seen 
from Below. 

1. Body. 2. Vertebral foramen. 
3. Transverse process. 4. Inferior 
articular process. 5. Spinous proc- 
ess. 6. Pedicel. 7. Lamina. 



The curves in the spinal column serve not only to give 
beauty to the outline of the body, but are so arranged that 
the direction of the line of shock falls outside of the brain, 
giving it security from injury from this source. 

The first two of the cervical vertebrae are very much 
modified to adapt them to their special function. The first 
of the cervical vertebrae is called the atlas. It surmounts 
the vertebral column, and articulates with the cranium. It 
is without spinous process and body. 

On its upper surface are two depressions for the reception 
of the occipital condyles of the cranium. The neural arch is 
large, and receives in its anterior portion the odontoid proc- 
ess, which is held in place by the check ligament (Fig. 98). 
The second cervical is called the axis. From its body arises 
the odontoid process (Fig. 99), which forms the axis of rota- 



180 



THE SKELETAL SYSTEM. 



tion of the head. The foramen in the transverse process are 
for the passage of the vertebral artery. 

Pectoral Girdle. — To the vertebral column are attached 
two girdles to the first dorsal; the pectoral girdle (Fig. 100), 
consisting of two f -shaped bones, the clavicles, and two flat, 
irregular bones, the scapulas. The clavicles (Fig. 100) 
articulate in front with the sternum, and posteriorly with 
the scapula. The scapula (Fig. 101) is very irregular and 
marked by ridges, the more prominent being called the 
spine. The ridges give attachment to muscles. The round 
cavity (glenoid cavity) in the scapula is made deeper by a 
rim of cartilage, and receives the head of the humerus. The 




Fig. 98. — The Atlas. 
1. Anterior tubercle. 2. Depression 
to receive the odontoid process. 3. 
Transverse process. 4. Sinus for ver- 
tebral artery. 5. Posterior tubercle. 
6. Lateral mass. 7. Posterior arch. 8. 
Anterior arch. 




Fig. 99. — The Axis. 
1. Odontoid process. 2. Su- 
perior articulating surface. 
3. Transverse articular proc- 
ess. 4. Foramen for verte- 
bral artery. 5. Inferior artic- 
ular process. 



large process projecting forward and articulating with the 
clavicle is the acromion process. The hook-shaped process 
is called the coracoid process. The scapula has no articula- 
tion posteriorly, but rests in the flesh, supported by muscles 
and ligaments, hence the ease of its dislocation. 

Pelvic Girdle. — The pelvic girdle (Figs. 100 and 105) 
consists of the ossa innominata, which articulate with the 
sacrum posteriorly. This forms a bony basin, the pelvis, 
which gives attachment to strong muscles, and also support 
to the abdominal viscera. The large foramen in the innom- 
inata is called the obturator foramen, and through it passes 
the obturator nerves and vessels; the greater part of the 
opening is filled by a membrane. 



THE UPPEH EXTREMITIES. 181 

The hemisphere-shaped cavity, called the acetabulum, is 
for the reception of the head of the femur. Like the glenoid 
cavity, it is deepened by a rim of cartilage. 

The sacrum and coccyx are really modified vertebrae. 

The sacrum (Fig. 105) is wedge shaped, articulating 
above with the last lumbar, below with the coccyx, and later- 
ally with the innominata. It has prominent intervertebral 
foramina. The coccyx is small, consisting of four or six 
bones which diminish in size from the sacrum. In the adult 
they usually become united into one bone. 

THE UPPER EXTREMITIES. 

The bones of the upper extremities are the scapula, clav- 
icle (forming the pectoral girdle), humerus, radius and ulna, 
carpal bones, metacarpal bones, and phalanges. 

The Arm. — This consists of one bone, the humerus (Fig. 
102), a long cylindrical bone consisting of a head, a slightly 
defined neck, a shaft, and its lower portion, two condyles. 

The head is hemispherical, and fits into the glenoid cavity. 
On the anterior surface of the lower extremity is the cavity 
(lesser sigmoid) for the reception of the coronoid process of 
the ulna, on the posterior is a large cavity (greater sigmoid) 
for the reception of the olecranon process of the ulna (Fig. 
103). 

Forearm, — The forearm (Fig. 103) consists of two bones, 
the radius on the thumb side and the ulna on the little 
finger side. The radius has at its upper portion a rounded 
head having a shallow depression which meets a slight pro- 
jection in the lower end of the humerus. Just below the 
head (the neck) there is attached a ligament in which the 
radius turns. The tubercle below the neck is for the attach- 
ment of the tendon of the biceps muscle. The lower end is 
broadened to make articulation with the bones of the wrist 
(carpal bones). The sharp projection (styloid process) is 
for the attachment of a ligament. The grooves on the pos- 
terior of the lower portion are for the passage of the tendons 
of the extensor muscles of the hand: * * Weo* 



^ 




12 w fl 
Fig. 103. — Right Radi- 
us and Ulna, Ante- 
rior View. 
1. Olecranon. 2. Great- 
er sigmoid cavity. 3. 
Lesser sigmoid cavity. 

4. Tubercle of the ulna. 

5. Coronoid process. 6. 
Nutrient foramen. 7. Ul- 
na. 8. Head. 9. Styloid 
process. 10. Articular 
surface. 11. Head of ra- 
dius. 12. Styloid process. 
13. Radius. 14. Nutrient 
foramen. 15. Bicipital 
tuberosity. 16. Neck. 
17. Head. 18. Articulat- 
ing surface. 

1 

2 




Fig. 101— The Scapula. 
1. Ooracoid process. 2. Su- 
prascapular notch. 3. Supra- 
spinous fossa. 4. Spine. 5. 
Infraspinous fossa. 6. At- 
tachment for teres major 
muscle. 7. Attachment for 




Fig. 104. — Carpal and Metacarpal 
Bones. 
1. Semilunar. 2. Scaphoid. 3. Tra- 
pezium. 4. Trapezoid. 5. Head of 
metacarpal bone (proximal). 6. First 
metacarpal bone. 7. Shaft. 8. Head 
(distal). 9. Unciform. 10. Os mag- 
num. 11. Cuneiform. 12. The pisi- 
form bone (not shown in cut). M u M 2 , 
M 3 , M 4 , and M 5 , metacarpal bones. 



15'- 




r— eo 



Fig. 100.— Chest, Pectoral Girdle, 
and Pelvic Girdle. 
1. Clavicle. 2. Scapula. 3. Ribs. 



the teres minor. 8. Rim of 4 Costal cartilage. 5. Vertebral col- 



the glenoid cavity, 
mium process. 



). Aero- umn. 6. Os irmominatum. 7. Sacrum. 
8. Sternum. 



10 

Fig. 102.— Right Hu- 
merus, Anterior 

View. 
1. Head. 2. Poste- 
rior bicipital ridge. 

3. Attachment for 
teres major muscle. 

4. Coraco-Brachiales 
(attachment). 5. An- 
terior border. 6. Me- 
dian border. 7. Coro- 
noid fossa. 8. Inter- 
nal condyle. 9.Troch- 
lear head. 10. Ra- 
dial head. 11. Exter- 
n a 1 condyle. 12. 
Radial fossa. 13. 
Lateral border. 14. 
Deltoid tuberosity. 
15. Pectoralis major 
(attach.). 16. Anteri- 
or bicipital ridge. 

17. Lesser tuberosity. 

18. Bicipital groove. 

19. Greater tuber- 
osity. 20. Surgical 
neck. 



LOWER EXTREMITIES. 183 

The ulna is longer than the radius. It is largest at its 
upper end to form the articulation with the humerus. The 
portion projecting backward is called the olecranon process. 
In the upper portion are two curved depressions (greater 
and lesser sigmoid cavity), the greater, for the reception of 
the humerus, and the smaller for the head of the radius. 
The hook-like process is called the coronoid process, which 
fits over the lower head of the humerus (Fig. 102). The 
lower end is flattened, and articulates with the radius. The 
long projection from the inner side (the styloid process) is 
for the attachment of a ligament. 

Carpus. — The carpus (Fig. 101), or wrist bones, are eight 
in number; in general form, cuboidal. Their names and 
position may be learned from Fig. 104. 

Metacarpal Bones. — These are situated beyond the carpal 
bones, being five in number, and form the palm of the 
hand. They are the long bones in form, being made up of 
two extremities and a shaft. The extremities articulate 
with the wrist bones, have facets for the reception of last 
row of carpal bones; the portion articulating with the first 
phalanges has a rounded head, giving more surface for artic- 
ulation and greater freedom of motion. 

Fingers. — The finger and thumb bones are known as pha- 
langes. In the fingers there are three rows; in the thumb, 
two. The first and second rows of bone resemble the meta- 
carpal bones in their form and structure, but they are shorter. 
The last row is flattened to adapt them to support the nails. 

THE LOWER EXTREMITIES. 

Femur. — The femur (Fig. 106), or thigh bone, is the long- 
est bone of the body. At its upper end is a hemispherical 
head supported by a well-defined neck, which joins the 
shaft at an obtuse angle. The projection from the upper 
part of the shaft is the greater trochanter ; beneath it on the 
opposite side is the lesser trochanter. These projections 
serve for the attachment of muscles. The shaft is round, 
strong, and marked by a prominent ridge (linea aspera). 





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LOWER EXTREMITIES. 185 

The lower end is expanded, and has two large condyles with 
rounded, smooth, articulating surfaces. Between the con- 
dyles is a depression for the patella. 

Patella. — This (Fig. 86) is a flat bone of a roundish tri- 
angular shape. It rests in the tendon which passes beneath 
it to join with the tibia. Anteriorly it is covered by the 
skin. In its nature and origin it is a sesamoid bone. 

Tibia. — This (Fig. 107) is the inner and the larger of the 
bones of the leg. Its upper surface is large, presenting two 
oval surfaces for articulation with the condyles of the femur. 
The lower extremity of the tibia is smaller than the upper, 
and it supports a large process {internal malleolus). The 
depression (fossa) on the outside is for the articulation 
with the fibula. 

Fibula. — The fibula (Fig. 107) is placed external to the 
tibia. It articulates with the head of the tibia. It is 
slender and weak, the extremities being relatively small. 
The lower extremity has a process (external malleolus). 

Tarsus. — The tarsus (Fig. 108) consists of seven bones, 
whose names may be learned from Fig. 108. Like those 
of the carpus, their general form is cuboidal. The tibia 
articulates with the astragalus; the heel is formed by the 
os calcis, to the posterior surface of which is attached the ten- 
don of Achilles. 

Metatarsal Bones. — They are five in number. They re- 
semble the metacarpal bones in their structure, but are larger. 

Phalanges. — These consist of the same number of bones, 
have the same arrangement and similar structure, as the pha- 
langes of the hand. 

Chemical Composition. — Bone is composed of earthy mat- 
ter about sixty-seven per cent, and of animal matter thirty- 
three per cent. These are so intimately blended and incor- 
porated that they can only be distinguished by chemical 
means, as burning or removal by acid. In case of removal 
of the earthy matter by acid, or the animal matter by burn- 
ing, the form of the bone is preserved. The proportion of 



186 THE SKELETAL SYSTEM. 

these two ingredients of the bone varies in different hones 
and in the same individual, and in the same hone at dif- 
ferent ages. The earthy material consists chiefly of calcium 
phosphate, with a small quantity of calcium carbonate, cal- 
cium fluoride, and magnesium phosphate, which make up 
about eleven of the sixty-seven per cent. 

Structure. — When examined without the aid of the micro- 
scope, we notice two kinds of bone tissue, often in the differ- 
ent parts of the same bone; the dense or compact, and the 
spongy, or cancellous bone. The compact is represented in 
the outer and inner surfaces of the cranial bones ; the spongy 
in the intervening bone. In the shaft of the long bones we 
notice the compact bone on the exterior and interior, and the 
spongy bone between. The extremities of the long bones are 
principally spongy bone. The cavity (Fig. 109) (medullary 
canal) in the shaft is filled with a fatty substance called 
marrow, which in the medullary cavity is called yellow mar- 
row, and consists chiefly of fat cells with numerous blood ves- 
sels ; there are also cells resembling the lymphoid corpuscles. 
In the spaces of the cancellous tissue is found a marrow 
called the red marrow. It is highly vascular, and maintains 
the nutrition of the spongy portion of the bones. 

The red marrow contains some fat cells, a large number 
of marrow cells, many of which resemble lymphoid cor- 
puscles, and have for their basis a small amount of fibrous 
tissue. There are also some nucleated cells of very much 
the same tint as the red corpuscles of the blood. 

There are a few large cells called giant cells (myelo- 
plaxes), probably derived from the overgrowth of the ordi- 
nary marrow cells. From the resemblance of the red cells to 
those of the red corpuscles it is thought that the marrow is 
a source of red corpuscles. 

Periosteum and Nutrient Blood Vessels. — The surface of 
the bone, except the part covered by the articular cartilage, 
is covered by a tough, fibrous membrane, the periosteum, and 
from its blood vessels the bone receives some of its blood 
supply, especially the compact portion. These go into the 




PLATE VII. 
Fig. 70. — A Diagram to Show the General Arrangement of the Fibers <>e 
the Cerebrospinal System. 
(Modified from Landois.) (From Ranney.) 
The shaded portions represent the collections of gray matter. On the left side of the diagram, the 
sensory fibers of the cms are traced upward from the spinal cord to various portions of the cerebrum; on 
the right side, the motor fibers are similarly represented. Numerals are used in designating the sensory 
and commissural fibers; the motor fibers are lettered in small type. The cortical layer is shown at the 
periphery of the cerebral seed n, with commissural fibers (1) connecting homologous regions of the 
hemispheres, and associating fibers (<*.«.) connecting different convolutions of each hemisphere, c.n. 
Caudate nucleus of the corpus striatum. L- N. Lenticular nucleus of the same. O- T. Optic thalamus 
of each hemisphere united to each fellow in the median line. e. g. corpora quadrigemia c. I. Claustrum, 
bin? to the right of the letters, c c. Corpus callosum, with its commissural fibers. 8. Fissure of sylvius. 
I*. Lateral ventricle, the fifth ventricle being shown between the two layers of the septum lucidum. V. 
the motor tract of the crus cerebri (basis cruris — crusta). T. The sensory tract of the crus cerebri 
^tegmentum cruris). Cf. The cerebellar fasciculus, e. The point of the decussation of the motor fibers 
of the spinal cord. /. The course of the decussating motor fibers of the spinal cord below the medulla, 
showing their connection with the cells of the anterior horns of the gray matter, and their continuation 
into the anterior roots of the spinal nerves (7>. o. Fibers which radiate through the caudate nucleus. 
/>. Fibers of the "internal capsule" C. Fibers which radiate through the lenticular nucleus. cL Fibers 
of the 'external capsule" 2, 3, 4, 5, 6, 7, 8, 9, sensory fibers radiating frr>m the tegmentum cruris to the 
cortex by means of various nodal masses of gray matter. 11. Course of the sensory fibers of the spinal 
cord 'shown by dotted line- f, intimately connected with the posterior root of the spinal nerve (12), and 
decussating at or near to the point of entrance into the spinal cord. In thi9 diagram, the direct pyram 
idal fibers are not shown, nor the gray matter of the pons. 



BONE. 187 

surface of the bone by numerous small openings ; from these 
openings the small blood vessels find their way to the Haver- 
sian canals. The periosteum not only serves as a means of 
nourishment to the bone, but also as a means for the attach- 
ment of tendons and ligaments. The long bones have, in 
addition, special nutrient vessels which enter the shaft of 
the bone, and find their way to the medullary canal, and, 
breaking up into numerous branches, supply the marrow. 
Other small vessels pierce the articular extremities for the 
supply of the cancellous tissue. 

Microscopic Structure. — While the cancellous and com- 
pact bone tissues differ in their coarse structure, they are 
essentially alike in their microscopic (Figs. 22 and 23) 
structure. 

When examined with a high power, the substance of the 
bone is found to contain many small, irregular spaces approx- 
imately fusiform in shape, known as lacunce, and containing 
the bone corpuscles or bone cells, and leading from these 
lacuna? are very minute canals (canaliculi) which anastomose 
with similar branches from other lacuna?. In longitudinal 
sections are seen round holes, which are sections of tubes 
which run for the most part longitudinally, but occasionally 
they give off cross branches. The average diameter of these 
tubes {Haversian canals) is one five hundredth of an inch. 
They are for the passage of blood vessels which enter the 
bone by the nutrient foramen. From the blood vessels of the 
Haversian canal, the lacunae and canaliculi absorb nutrient 
matter, and convey it more intimately to the very substance 
of the bone which they traverse. 

Development of Bone. — As to their mode of development 
bones may be divided into two classes : — 

1. Those which are formed (ossified) direct, from the 
first, in membrane or fibrous tissue; e. g., parietal and 
occipital bones. 

2. Those which, previous to ossification, were hyaline car- 
tilage ; e. g., humerus and femur. 

The ossification of bone is too complex to be described 



188 THE SKELETAL SYSTEM. 

here. Those desiring to know more about it may read the 
footnote. 1 

From the study of the note just given it will be seen 
that the terms " ossification in cartilage," and " ossification 
in membrane" are apt to be misleading, since they seem to 
imply two processes radically distinct. The process of ossi- 
fication is the same, however, be it cartilage or membrane, 
being from membrane, in each case from the perichondrium, 
or periosteum. In the development of a bone like that of 
the femur, which may be taken as the type of cartilage ossi- 
fication, the lime salts are first deposited in the cartilage ; 
this calcified cartilage, however, is gradually and entirely re- 
absorbed, being ultimately replaced by bone from the perios- 
teum, till in the adult structure nothing but bone is left. In 
the ossification of cartilage, calcification of the cartilaginous 
matrix precedes the real formation of bone. We should 
therefore make a distinction between ossification and calci- 

iThe ossification of bone may be divided into the following six stages:— 

1. The enlargement and proliferation of the cartilage cells and the formation 
of trabiculae by the deposit of lime salts in the matrix of the cartilage and the 
change of the perichondrium to the periosteum (stage of Proliferation and 
Calcification). 

2. Processes are given off from the cellular (osteogenetic) layer of the perios- 
teum containing blood vessels which grow out into the substance of the cartilage, 
the process beginning at the centers of ossification and spreading up and down the 
shaft, etc., so that the cartilage which contains no blood vessels becomes grooved 
by a network of blood vessels (stage of Vascularization). 

3. The arrangement of the cells of the primary marrow in contiguous layers 
like epithelium on the trabeculae (calcified), depositing a layer of bone and 
ensheathing them. This is followed by the absorption of the trabecule by 
means of cells called osteoclasts, leaving the bone spongy and composed of young 
bone, the calcified cartilage being completely absorbed (stage of Substitution of 
Embryonic Spongy Bone for Calcified Cartilage). 

4. The embryonic spongy bone is only a temporary tissue, the periosteum 
form around the embryonic bone, true bone, by the deposit at the circumference 
of the shaft. The embryonic spongy bone is absorbed through the agency of the 
osteoclasts; the trabeculae absorbed, the cavity thus formed is called the " medul- 
lary canal of the shaft (stage of Substitution of Periosteal Bone for the Primary 
Embryonic Bone). 

5. The work of absorption continues until all the bone — spongy bone — is 
absorbed. At the same time the periosteum is depositing new layers to those 
already deposited. The medullary canal is enlarged, and its boundary wall of 
periosteal bone thickened (stage of Absorption of the Inner Layers of Periosteal 
Bone). 

6. The formation of compact bone now takes place, the irregular walls of the 
areolae being absorbed ; the osteoblast which line them forming themselves into 
concentric layers, each in its turn becoming ossified, forming a Haversian canal 
(stage of Formation of Compact Bone). 



BONE. 



189 



fication. Calcification is simply the infiltration of an animal 
tissue with lime salts, being a change of chemical composition 
rather than structure, while ossification is the formation of 
true bone, a tissue more complex and more highly organized 
than that from which it is derived. Compare the structure of 
hyaline cartilage with that of bone (Fig. 20 and Fig. 23). 

Centers of Ossification.— In all bones ossification begins 
at one or more points called centers of ossification. The 
long bones usually 
have at least three cen- 
ters, one for the shaft 
(diaplujsis), one for 
each articular extrem- 
ity (epiphysis), but 
besides these primary 
centers there are cen- 
ters for the various 
processes. 

Articulations.— The 
union between two or 
more bones is called a 
joint, or articulation. 
These, as we have seen 
from the examination 
of the skeleton, are of 
great variety, making 
possible the varied 
movements o f which 
the body is capable. 

Structure of Joints. 
— The structure of the 
joint is dependent 
upon the kind a n d 
amount of motion it permits. In immovable joints, as that 
of the parietal bones, the bones are in close contact, being 
separated only by a thin layer of fibrous membrane (the 
sutural ligament). 




Fig. 109.— 1. Head. 2. Shaft. 3. Medullary 
canal. 4. Periosteum. 5. Cancellous tissue or 
spongy bone. 6. Compact tissue. 7. Arches of 
cancellous tissue. (Brinckley, C. W. B.) 



190 THE SKELETAL SYSTEM. 

In movable joints, as we have seen, the bones entering 
into the joint are expanded at the articulating end, the head 
of which is covered by a cap of cartilage called the articular 
cartilage. The surface to which cartilage is attached is called 
the articular lamella. In joints like that between the body 
of the vertebrae there is cartilage between the articulating 
surfaces, called the interarticular cartilage. 

In the movable joints, the parts are bound by bands of 
tissue (ligaments) of various forms. In those joints in 
which firmness rather than motion is needed, the proportion 
of white fibrous tissue is greater; but when flexibility and 
elasticity as well as firmness are needed, the proportion of 
yellow elastic tissue is the greater, and in some cases the 
ligament consists entirely of yellow elastic tissue ; as in the 
ligaments which hold the arches of the vertebras. On the 
surface of the bone in movable joints there would be fric- 
tion, and to prevent this the articulating surfaces are cov- 
ered by a delicate membrane (synovial) of connective tissue 
with branched connective tissue corpuscles. This membrane 
secretes a thick, viscid, glary liquid, like the white of an egg y 
and is called synovia. 

The synovial membranes are of three varieties: (1) 
articular, like that found in the movable joints; (2) bursal, 
where they are interposed between surfaces which move upon 
each other, as in the gliding of a tendon or a muscle; (3) 
vaginal (sheath synovial membrane), where tendons move 
through osseous or membranous canals, as in the flexor ten- 
dons. 

Classes of Articulations. — Articulations may be grouped 
into three general classes: immovable (synarthrosis), mixed 
(amphiar thro sis) , and movable (diarthrosis). For more 
important varieties of these classes, see diagram of the artic- 
ulations. 



DIAGRAM OF THE ARTICULATIONS. 

(Modified from Gray's Anatomy.) 



Articulations 
whose surfaces are 
connected by fi- 
brous membranes 
or cartilage and 
without any syno- 
vial cavity, and 
permitting no mo- 
tion {Synarthrosis). 



By interlocking 
processes and in- 
dentations (Su- 
tura). 



- Mixed articula- 
tions with little 
motion {Amphiar- 
throsis). 



Free movement, 
well-developed sy- 
novial membrane 
(DiartJirosis). 



Bone joining by indented edges 
{Sutura vera), as the parietal 
bonss. 

Bones joining by rough sur- 
faces {Sutura notha), as the 
articulation between the parie- 
tal and squamous portion of 
the temporal bone. 
The joining of a thin plate of one bone into 
the fissure of another {Schindylesis), as the articu- 
lation of the sphenoid with the vomer. 

By the insertion of a conical process into a 
socket {Gomphosis), as the teeth in the alveolar 
process. 

By contact of surfaces as in the epiphysis of a 
bone and its expanded portion {Synchondrosis), 
as in the inferior maxillary bone and in the 
epiphysis of the long bones. 

Surfaces connected by fibrocartilage, no syno- 
vial membrane, limited motion {Symphysis), as 
the articulation of the bodies of the vertebrae. 

Surfaces connected by an interosseous mem- 
brane {Syndemosis), as the articulation between 
^ the tibia and fibula. 

Motion limited to two directions, forward and 
backward like that of a hinge {Oinglymus), as the 
articulation of the humerus and ulna. 

By a pivot-process turning in a ring {Trochoides)-, 
the articulation of the radius with the ulna, and 
the odontoid process of the axis with the atlas. 

By an ovoid head in an eliptical cavity, permit- 
ting movement in various directions, but no axial 
motion {Condyloid)-, wrist joint. 

The concave surface of one bone fitting over 
the convex surface of another like a saddle 
{Reciprocal Reception)-, the joint between the 
carpal and metacarpal bones of the thumb. 

Globular head of one bone received into the 
cup-shaped cavity of another {Enarthrosis); the 
head of the femur with acetabulum. 

The articulating surfaces gliding on each other 
{Arthrodia); carpal and tarsal joints. 

191 



CHAPTER VII. 

THE ALIMENTARY SYSTEM. 

DISSECTION. 

I. Kill a rat or cat with chloroform. (For method, see 
Appendix.) 

II. Dissect the skin from the ventral portion. In the 
region of the neck look for, and observe : — 

A. A body (one of the salivary glands, the submaxillary) 
(Fig. 119), close to the middle line of the submaxillary bone. 

1. Observe shape, size, etc. 

2. Lift up and trace the duct to its opening. 

B. The large gland (parotid) (Fig. 119) situated in 
front of the ear and reaching to the angle of the jaw. 

1. Observe as above. 

2. Trace its duct. 

C. Remove muscles, etc., covering the trachea (Fig. 5) 
and larynx. Cut away the front and side walls of the chest 
and abdomen, and remove the larynx, trachea, lungs, and 
heart. Observe : — 

1. A slender muscular tube, noticing its relations and 
tracing its direction in the chest, and how it passes (Fig. 5) 
through the diaphragm. 

2. The relation of the abdominal viscera (liver, stomach, 
etc.). 

D. Turn the liver out of the way, and continue the trac- 
ing of the esophagus to stomach. Now observe carefully 
the stomach : — 

1. Size, shape, position. 

2. Its relation. 

3. How supported ? 

4. The thin membrane attached to it and hanging down 
so as to cover up the other abdominal viscera. This mem- 
brane is called the omentum, and is a part of the peritoneum. 

E. Now follow and carefully unravel the coils of the 
intestines, and as far as possible, spread out the delicate 
membrane (mesentery) which clings to them. 

192 



DISSECTION. 193 

1. Look in the fat of the mesentery for blood vessels and 
lacteals. 

2. Observe the termination of the small intestines. 

.3. Notice how the large intestines begin by a sac-like 
projection (ccecum). Do you find anything attached to the 
coecum ? 

4. Observe the larger intestine on the other side. Cut 
away the front of the pelvis so as to trace it to its terminus. 
The lower portion of the intestine is the rectum. The portion 
between the coecum and rectum is the colon. 

5. Carefully note direction and relation of the intestines. 

F. Spread out the portion of the mesentery lying in the 
concavity of the first coil {duodenum) of the small intestines. 

1. Observe the branching glandular mass, pancreas 
(Fig. C). _ 

2 C Notice relation. 

3. Trace duct to its opening. 

G. Examine large vein that enters the under side of the 
liver by several branches. Close by its side notice a duct 
(gall duct) formed by two main branches, and trace it to 
the small intestines. 

H. Look for an elongated red body (spleen) (Fig. 6) 
just behind, and to the left of the stomach. 

1. Has it a duct? 

2. Are there any blood vessels going to it % 

I. Tie the esophagus (Fig. 5) as high up as possible, and 
tie the rectum as low as possible. Then cut between the 
string and the body. Sever the mesenteric bands, etc., and 
also the other portions by which the canal is fixed. Eemove 
the whole tube; cut away the mesentery; spread it out at 
full length. 

1. Notice relative diameter and length of its various 
parts. 

2. Length as compared with that of the animal. 
J. Open the stomach. 

1. Examine the orifices. 

2. The mucous membrane. (Use a lens of l/o-inch focus.) 
Demonstrations. — 1. Obtain from your butcher two or 

three inches of the small intestine of a calf (just killed). 
Place in fifty per cent alcohol for twenty-four hours. Then 
open under water, and examine with lens of a magnifying 
13 



194 THE ALIMENTARY SYSTEM. 

power of twenty or thirty diameters. What are the little 
papilla-like bodies ? 

2. Cut from the larger end of the stomach a piece about 
one half inch square. Wash for a few minutes in normal 
salt solution; with small pins fasten it to a piece of cork, 
putting muscular surface downward, and slightly stretching 
it. Pass it through sixty-, eighty-, and ninety-per-cent alco- 
hol, leaving from one to two hours in each grade of alcohol. 
Color by keeping in hematoxylin for one or two days until 
well stained. After staining, remove to ninety-five-per-cent 
alcohol, in which it should remain until well hardened ; then 
imbed, and make section, and mount as directed in the 
Appendix. 

3. Take a similar piece from near the entrance of the 
stomach into the duodenum, and treat as above, and examine. 
What difference do you note in these two portions ? 

4. Cut off one or two inches of the duodenum and care- 
fully wash by moving the piece back and forth in a normal 
salt solution, being careful not to injure the mucous mem- 
brane by undue pressure. Make cross-section of the pieces 
one-half inch long, and harden, stain, and mount as in 
experiment. 

5. Carefully note: (a) the permanent folds (valvules 
conniventes), making partial rings around the interior of 
the intestine; (b) the prominent projecting hair-like proc- 
esses (villi). Try to get both longitudinal and cross-section 
of the villi; (c) the glands (crypts of Lieberhuhn) dipping 
into the mucous membrane ; (d) the glands (glands of Brun- 
ner) in the submucous tissue; (e) the patches of granular- 
looking tissue (solitary glands) ; (/) muscular fibers (mus- 
cularis mucosae) beneath the mucous membrane. 

6. Examine in a similar way different parts of the small 
intestine. In what parts are the glands of Brunner most 
numerous ? In what parts are they not found ? Where are 
the solitary glands most numerous ? Do you find the solitary 
gland sometimes occurring in patches (Peyers patches) ? 

7. Examine in a similar way the larger intestine. Note 
difference in structure. Do you find the following in the 
larger intestine: villi, Peyer's patches, and valvulse conni- 
ventes ? 

8. Take a small portion of a fresh liver, and tease out 



EXPERIMENTS AND DEMONSTRATIONS. 195 

in normal salt solution. Examine under high power, and 
note structure of the connective tissue and liver cells. 

9. Macerate portions of the liver of the rabbit for four 
or live days in a two-per-cent solution of potassium dichro- 
mate and then in ninety-per-cent alcohol for one or two days. 
Stain in picrocarmine. Prepare a slide for examination, 
and examine under two-thirds and one-sixth objectives. 

10. Inject the liver by means of the portal vein, using 
a carmine gelatin mass. Examine various sized sections of 
the liver. Make as thin a section as possible with a sharp 
razor in a moistened normal salt solution, and mount in 
glycerin, and examine with one-fourth objective. 

11. Prepare as directed in Experiments 8 and 9 a por- 
tion of the pancreas and spleen, noting in each case the dif- 
ference in structure. 

12. Compare the structure of the salivary glands and 
pancreas. Also compare the structure of the parotid, sub- 
lingual, and submaxillary glands. These may be prepared as 
directed in Experiments 8 and 9. 

13. Procure from the druggist a sheet of blue litmus 
paper and one of red litmus paper. Cut into strips one- 
fourth inch wide and two or three inches long. Put into 
a test-tube a few drops of sulphuric acid, and dilute with 
many times its own volume of water. Dip the end of a 
piece of blue litmus into the acid. Notice the change of 
color. In another test-tube put fifteen or twenty drops of 
ammonia diluted to several times its volume. Test this with 
a piece of red litmus paper. Notice change of color. When 
substances change blue litmus to red, they are said to be 
acid; and when they change the red to blue, they are 
called alkaline. 

Test some distilled water (fresh rain water will do) with 
both red and blue litmus paper. Does it change the color 
of either ? When substances do not affect either the blue 
or the red, it is called neutral. 

Are the following acid, alkaline, or neutral? a solution 
of common salt, a solution of baking powder, a solution of 
wood ashes, a solution of sugar, the saliva, gastric juice, bile, 
vinegar, sour milk, and cream of tartar. 

11. Collect eight or ten c.c. of saliva in a test-tube, and 
let stand until the turbidity has settled down into a sediment. 



196 THE ALIMENTARY SYSTEM. 

Add strong acetic acid until a stringy mass separates. Shake 
the tube gently, which will cause the stringy mass to form 
a lump, when it can be removed. The stringy mass is mucin. 

15. Filter the liquid after you have removed the mucin, 
the precipitate left on the filter indicates the amount of 
proteids present in the saliva. Test some fresh saliva with 
Millon's reagent (see Appendix). 

16. Add to some saliva in a test-tube a few drops of 
ferric chloride. See if the color disappears on the addition 
of a few drops of a solution of mercuric chloride (corrosive 
sublimate). The blood-red color is due to the presence of 
potassium sulphocyanate in the saliva. 

17. Add to some saliva in a test-tube a few drops of a 
solution of silver nitrate (lunar caustic). A white precip- 
itate indicates the presence of chlorides in the saliva. 

18. Test the saliva for sodium and potassium (see Ap- 
pendix) . 

19. Mount a section of the liver (fresh). Add by means 
of a pipette to the side of the cover glass a drop of strong 
iodine; the cells containing glycogen will be colored deep 
brown-red. 

20. Macerate a piece of fresh liver in distilled water for 
five or six hours (having first washed the piece to remove the 
blood). Strain the solution through a clean cloth. To a small 
portion in a test-tube add a few drops of a solution of potas- 
sium iodide, and then a small amount of chlorine water. 
The port wine-red color produced is due to the glycogen in 
the first solution. 

THE ALIMENTARY SYSTEM. TEXT. 

Need of Organs of Alimentation. — Food is needed to 
maintain the heat of the body, to furnish material for nerv- 
ous and muscular activity and the various vital processes. 
Before it can get to the tissues where it is needed, it must get 
into the blood. Most of our food is not soluble, and before 
it can enter the blood it must be made so. To make the food 
soluble is the chief purpose of digestion, and the system of 
organs by which this is accomplished is the alimentary canal, 
salivary glands, pancreas, and liver. 

Relation of the Alimentary Canal The tubular system 

is divided into five principal divisions, according to the func- 



EXPERIMENTS AND DEMONSTRATIONS. 107 

tions performed by the part: alimentation, respiration, cir- 
culation, secretion, and excretion. 

Tissues of Alimentary Canal. — The principal tissues of 
this canal are muscular, connective, mucous, and in the 
abdominal cavity there is a fourth, the serous. 

The Mucous Membrane. — This membrane lines the alimen- 
tary canal, the respiratory tract, the glands and tubes opening 
into the alimentary canal, and all other tubes communicating 
with the air. 

The mucous membrane is in reality a modified skin re- 
flected inward to line the various tubes which have external 
openings, and changed in its structure to adapt it to its new 
functions. 

Like the skin, it is composed of two principal layers, the 
outer, or epithelial, whose cells are of various forms, — 
squamous (often arranged in several layers), cubical, col- 
umnar, and ciliated; and the inner, or corium, consisting 
of connective tissues, either simple, areolar, or containing 
a greater or less quantity of lymphoid tissue, and supplied 
with a dense network of capillaries. The mucous membrane 
is connected with organs which it lines by connective tissue, 
which is sometimes very abundant, forming a well-marked 
layer, called submucous membrane. 

In the epithelium are imbedded litttle glands which se- 
crete the fluid (mucus) which moistens the membrane. We 
shall notice that as the mucous membrane has new 
functions to perform, it becomes modified for its varied 
work. 

The Mouth. — The alimentary canal begins with the 
mouth, or buccal cavity. The mouth is nearly oval in shape. 
It is bounded in front by the lips, on the sides by the cheeks, 
and possesses the upper and lower jaw, above by the hard 
palate, below by the tongue and mucous membrane, behind 
by the soft palate. The free border of the soft palate is called 
the uvula. Examine the mouth by the aid of a looking-glass. 
The opening from the mouth to the pharynx is called the 
fauces. 



198 



THE ALIMENTARY SYSTEM. 



The Pharynx. — This (Fig. Ill) is the cavity just back 
of the mouth and nasal passages. It is four inches in length, 
extending from the under surface of the skull to the space 
between the fifth and sixth cervical vertebra?. It has seven 

openings : — 

1. Two from the nasal pas- 
sages — posterior nares. 

2. Two to the ears — Eusta- 
chian tubes. 

3. One to the mouth — fauces. 

4. One to the larynx — glottis. 

5. One to the esophagus — be- 
low. 

It has three coats, the outer 
muscular, consisting of two sets 
of fibers, longitudinal and trans- 
verse; a middle fibrous, and an 
inner mucous. The mucous 
membrane is covered as low down 
as the floor of the nares with cil- 
iated epithelium. 

The Tonsils. — These are two 
oval bodies situated in the spaces 
between the anterior and posterior 
pillars of the fauces. Each tonsil 
consists of a mass of lymphoid 
tissue. The free surface is cov- 




FiG. no. 



Alimentary 



Canal. 
1. Stomach. 2. Duodenum (be- 
ginning of small intestines). 3. 
Small intestines. 4. Ileum (last 
portion of small intestines). 5. 
Caecum. 6. Vermiform appendix. 

IwiTolo^^^enaVcoton: ered with stratified epithelium, 
l%. Si 8 g Ti d o. fl a e nd n. &££££: perforated by twelve to fifteen 
tines. 12. Spleen. orifices, which lead into small 

cavities, or crypts, from which branches go out into the 
substance of the gland. In these follicles, or branches, 
active multiplication of lymph cells occurs, which pass 
through into crypts, and mingle with the saliva as salivary 
corpuscles. 

This viscid secretion aids in deglutition by lubricating the 
bolus of food as it passes in the second stage of the act of 
deglutition. 



ORGANS. 



109 



The Esophagus, or Gullet. — This is the continuation of 
the pharynx, and extends to the stomach, heing in length 
about nine inches. It lies in front of the spine and back of 
the trachea, its general direction being vertical. Its coats 
are similar to those of the pharynx. There is, however, a 
marked modification in the mucous membrane, the little 
glands secreting 
an oily fluid (eso- 
phageal). They 
are most numer- 
ous in the lower 
part of the tube. 

The Stomach. 
— Before reach- 
ing the stomach, 
the esophagus 
passes through 
the diaphragm. 
It terminates at 
the cardiac ori- 
fice. At this 
point the alimen- 
t a r y canal be- 
comes very much 
enlarged i n t o a 
pouch-like organ 

/ / 7 v 1. Upper part of pharynx. 2. Opening of the Susta- 
in Stoma C/i J. chian tube. 3. Soft palate. 4. Fauces. 5. Epiglottis. 
rri . . . 6. Glottis. 7. Esophagus. 8. Trachea. 9. Posterior 
UllS IS Situ- nares. 10. Nasal fossa. 11. Base of cranium. 

ated iii the upper and left side of the ventral cavity, below 
the liver, and above the transverse colon. 

Its shape resembles that of a bagpipe, having the 
greater curve below, and the larger end (splenic), or fun- 
dus, to the left, and the smaller (pyloric), Or antrum, to the 
right. 

The size varies with the individual and the degree of dis- 
tension ; when moderately distended, the transverse diameter 
is about twelve inches. 




Viq. 111.— The Pharynx. (From Yaggy's Anatom- 
ical Study.) 



200 THE ALIMENTARY SYSTEM. 

Openings of the Stomach. — They are the esophageal, or 
cardiac, and the intestinal, or 'pyloric. At the latter orifice 
the oblique muscular fibers interlace from different direc- 
tions, forming a kind of sphincter muscle, and with the 
mucous membrane form a kind of valve. 

The coats are four: Serous (derived from the peri- 
toneum), muscular, areolar (or submucous), and mucous. 

Serous Membranes. — These membranes differ from the 
mucous membranes both in structure and function. 

Very generally they are closed sacs with one portion at- 
tached to the walls of the cavity they line, and the other 
reflected over the organ or organs contained in the cavity, so 
placed between and over the organs that they may move 
upon each other without friction. These membranes are 
thin, transparent, glistening; lined on their inner surface 
by a single layer of endothelial cells, supported upon a 
matrix of fibrous connective tissue, with network of fine 
elastic fibers. They secrete a fluid very closely resembling 
lymph. Such is the membrane (peritoneum) which lines 
the abdominal cavity and forms the serous coats of its vis- 
cera (Fig. 113). 

Muscular Coat of Stomach. — This coat lies just beneath 
the serous. It consists of three layers — the outer of longi- 
tudinal fibers, the middle of circular or transverse fibers, 
which are more numerous at the pyloric end, and the oblique, 
found chiefly at the cardiac portion. The muscles are more 
strongly developed in the antrum than in the fundus. 

Sub-Mucous Coat. — This membrane lies between the 
muscular and mucous coats, and forms their connection. It 
is highly vascular; i. e., having a large number of blood 
vessels. 

Mucous Coat of Stomach. — This is the inner lining of 
the stomach. It is smooth, velvety, and of a pinkish tint. 
It rests upon a layer of loose cellular tissue (the sub- 
mucous tissue), and is smooth, soft, and velvety, of a pale 
pink color, and when the process of digestion is not going 
on ? is thrown into numerous folds, or rugce, which dis- 



ORGANS. 



201 



appear when the stomach is distended, as in the act of diges- 
tion. A fine connective tissue forms the basis of the mucous 
membrane, resembling in its structure adenoid tissue, and 
in which is supported the tubular glands. In various parts 
of this coat, just beneath the glands, are masses of adenoid 
tissue, called lymphoid follicles. In the deepest part of 
the m ucous 
membrane is a 
layer of circular 
and longitudi- 
n a 1 unstriped 
muscular fibers, 
known as the 
musculo ris mu- 
cosa?, separating 
the mucous 
membrane from 
the submucous. 
O n exami- 
nation by a low- 
power lens, the 
mucous m e m - 
brane of the 
stomach pre- 
sents a honey- 
c o m b appear- 
ance, produced 
by shallow de- 
pressions of one 

two- hundredth FlG - 112 - ~ The Peritoneum. 

1. Bursa of the omentum. 2. Pancreas. 3. Duodenum. 

to One three- 4. Rectum. 5. Bladder. 6. Small intestines. 7. Omen- 
tal sac 8. Transverse colon. 9. Greater omentum. 10. 

hundred-and-flf- Stomach. 11. Lesser omentum. 12. Foramen of Wins- 
low (epiloicum). 13. Liver. 14. Diaphragm. 

tieth of an inch 

in diameter, but near the pylorus they are larger, being 
one one-hundredth of an inch. These depressions (alveoli) 
are separated by slightly elevated ridges, which sometimes, 
in morbid conditions, bear minute vascular processes, resem- 




20: 



THE ALIMENTARY SYSTEM. 



bling villi. Leading into these alveoli from below are tub- 
ular glands, of which there are two varieties, (1) cardiac 

and (2) pyloric. 

Cardiac Glands (Fig. 113) 
are found throughout the en- 
tire cardiac portion of the 
stomach. They are arranged 
in groups of four or five, the 
groups being separated by a 
fine connective tissue. Thev 
consist of a duct (alveola), 
which forms about one sixth 
the length of the gland, and 
into which open two or three 
tubes. 

The duct is lined with 
columnar epithelium. The 
gland proper, or the portion 
below the duct, consists of 
the upper third, the neck, 
and the lower two thirds, the 
body. The narrow neck is 
lined with granular cubical 
cells, which are continuous 
with the columnar cells of 
the duct. Between these cells 
and the membrane proper 
(Fig. 113) there are large 

oval granular cells, each with 

Fig. 113. — Vertical Section of Mu- • , 1 -,-, -, 

cods Membrane of the cardiac a prominent nucleus, called 

End of Stomach. ' / 7 77 

a. Duct of cardiac gland with columnar parietal, Cells. 

epithelium becoming shorter as the cells mi r.-j^ /? .1 „i QTir l ,* Q 

are traced downward, n. Neck of gland Ihe body 01 the gland IS 

tubes with central and parietal or so- • i 

called peptic cells, to. Fundus with Wider 

curved csecal extremity — the parietal 




called peptic cells, *>: Fundus with wiuer than the neck, and 

curved csecal extremity — the parietal -, -. i 

cells are not so numerous here. X 400. ends in a rOTHlded expansion, 

(Klein and Noble Smith.) « , , . , . 

or fundus, which terminates 
near the muscularis mucosae. The structure of the gland 
changes as it approaches the pylorus, the ducts become 



GLANDS OF THE STOMACH. 



203 



longer, and the tube proper becomes shorter, with occasional 
branches of the fundus of the body. 

Pyloric Glands. — These (Fig. 11-1) are situated in the 
pyloric portion of the stomach. Their ducts are longer ; the 
tubes which open into the ducts have very short necks (gen- 
erally two or three in number). The cells lining these glands 
are similar to those of the cardiac, with the exception that 
they have no parietal cells. As the 
glands near the pyloric orifice, they 
become more convoluted and deeply 
seated, becoming continuous with the 
glands of Brunner of the duodenum. 

Lymphatics. — These surround the 
gland tube to a greater or less ex- 
tent. Kear the fundus of the peptic 
glands are found masses of lymphoid 
tissue, resembling the solitary glands 
of the intestines, and which form dis- 
tinct follicles. 

Blood Vessels. — These find their 
way to the mucous membrane by way 
of the submucous, in which they send 
branches upward between the closely 
packed gland tubes, anastomosing 
around them by means of a fine capil- 
lary network with oblong meshes. 

» -i .-, , n . . , 8. Free surface, d. Duct of 

Around, tne orinces of the tubes pyloric gland, n. Neck of 

-, . the gland. m. The gland 

is a dense network oi larger canil- alveoli, m. m. Muscuiaris 

, . , . . . . & 1 mucosae. (Klein and Noble 

lanes, which is continuous with the Smith.) 
deeper plexus just described. It is from this superficial net- 
work that the veins chiefly take their origin. 

Nerves.— These (Fig. 115) are derived from the branches 
of the pneumogastric and sympathetic, forming plexuses in 
the submucous and muscular coats, containing numerous 
ganglia. Study Fig. 115 carefully. 

The Intestines. — At the pyloric orifice the alimentary 
canal becomes contracted into a long tube (intestines), about 




Fig. 114.— Vertical, Section 
Through Pyloric Glands. 



204 



THE ALIMENTARY SYSTEM. 



twenty-five feet in length, divided into two portions distin- 
guished according to size, large and small. 

Oe Coats of the 

in r.i; 

Smaller Intes- 
tines. —These 
like the stom- 
a ch, have 
four coats — 
the serous, 
muscu- 
lar, submu- 
cous, and mu- 
cous. 

Serous Coat. 
— This is de- 
rived from 
the reflection 
of t h e peri- 
toneum en- 
circling 
it, as repre- 
s e n t e d in 
Fig. 112, so 
as to leave an 
opening 
through 
which the 
blood vessels 
enter. 

Muscular 
Coats.— These 
consist of an 
internal, cir- 
cular, and an 
external 




RcU 



Fig. 115. 



Diagram of the Nerves op the Alimentary 
Canal in the Dog.i 
Oe to Ret. Alimentary canal. L. V. Left vagus nerve end- 
ing in front of the stomach, r. I. Recurrent laryngeal nerve 
supplying the upper part of the esophagus. R. V. Eight 
vagus joining the left vagus in the esophageal plexus, oe. pi, 
and passing down to supply the posterior part of the stomach 
and continuing as the B.' v.' to join the solar plexus, repre- 
sented in the figure as a single ganglion and connected with 
the inferior mesenteric ganglion (or plexus), a. Branches of 
solar plexus to stomach and small intestines. Spl. maj. 
Larger splanchnic from the thoracic ganglia and the rami 
communicantes, r. c. of the 6th to 9th dorsal nerves. Spl. min. 
Smaller splanchnic nerve from the 10th and the 11th dorsal 
nerve. The larger and smaller splanchnicsboth join the solar 
plexus, from which they pass to the alimentary canal, c. r. 
Nerves from the ganglia of the 11th and the 12th dorsal and 
the 1st and 2d lumbar nerves. These nerves join the mesen- 
teric ganglia from which they pass by the hypogastric nerve 
and the hypogastric plexus to the circular muscle of the rec- 
tum, n. hyp. Hypogastric nerve, pi. hyp. Hypogastric plexus. 
I. r. Nerves from the 2d and 3d sacral nerves, S. 2, S 3 (nervi 
erigentes), passing by the- hypogastric plexus to the longitu- 
dinal muscles of the rectum. 



i" It was not observed until too late that in the diagram of the nerves of the 
alimentary canal in the dog, twelve dorsal nerves had been represented. The 
figure makes no pretense to anatomical exactness; but it would have been better 
to represent either thirteen or fifteen dorsal nerves."— Foster. 



INTESTINAL MEMBRANES. 205 

layer of longitudinal fibers, of which the former is usu- 
ally the thicker. They are provided with lymphatic ves- 
sels, which form an independent system from that of the 
mucous membrane. Between these muscular coats is a nerve 
plexus (plexus of Auerbach). 

Submucous Coat. — The coat lies just beneath the mucous 
coat, and is similar to that described in the stomach. It is 
provided with numerous blood vessels and lymphatics. In 
it there is a fine plexus, consisting principally of non-medul- 
lated fibers, having ganglia at the nodal points, forming the 
plexus of Meissner. This plexus of nerves is found in the 
submucous membrane, from the stomach to the end of the 
large intestines. 

Mucous Membrane. — In no part of the alimentary tract 
does the mucous membrane have so varied a function to per- 
form as in the intestines, and we find it, for this reason, much 
more complex or modified. In general structure it resembles 
that of the stomach, having in its deeper part two layers of 
muscular fibers, circular and longitudinal, forming the mus- 
cularis mucosa?. 

The mucous membrane is thrown into permanent folds, 
called valvulce conniventes. These begin in the duodenum 
about two inches from the pylorus, become larger and more 
numerous just beyond the entrance of the bile duct, and are 
thickly arranged and well developed throughout the jejunum; 
then they gradually diminish in size and number, and cease 
near the middle of the ileum. They are formed by the 
doubling inward of the mucous membrane so as to form 
crescent-shaped folds, each individual fold not extending 
more than two thirds around the circumference of the wall. 
To get a proper idea of these, it is best to prepare a portion 
of the intestine, as directed in the experiments. 

These permanent folds serve two very important func- 
tions : (1) They increase the surface of the mucous membrane 
for absorption and secretion; (2) they retard the passage 
of the liquid contents of the intestines. 

Glands. — These are of three principal varieties, the crypts 
of Lieberkuhn, glands of Brunner, and glands of Peyer. 



206 



THE ALIMENTARY SYSTEM. 



The crypts of LieberMihn, or intestinal follicles, are 
simple tubular depressions in the mucous membrane, and are 
thickly distributed over the whole surface of both the small 

and large intestine. In the 
small intestine they are vis- 
ible only by means of a low- 
power lens ; they are large in 
the large intestines, and in- 
crease in size as they near 
the end of the intestine; in 
the rectum the openings are 
visible to the naked eye. 
They vary in length from 
one one-hundred-and-eighti- 
eth to one sixtieth of an 
inch. The mucous membrane 
by which they are lined is 
essentially like that of the 
intestinal membrane, but hav- 
ing numerous goblet cells. 

The Glands of Brunner. — 
These are found only in the 
duodenum, at the commence- 
ment of which they are 
thickly set, and diminish 
gradually along the course of 
the duodenum. They are sit- 
uated beneath the muscularis 
mucosae, imbedded in the sub- 
mucous tissue. Each gland 
consists of a branched and 
convoluted tube, resembling 
in structure the pyloric 




-?-••-'• - : - ' > ',, > 

•>- ^ , > < ■ > 

. ■ : i - -- : --v> 

Fig. 116. — Mucous Membrane op 

Small Intestines. 

1, 2, 3. Mucous membrane. 1. Villi. 2. 

Intestinal gland (crypts of Lieberkiihn). 

i£^t^s^^^rrvsssi g lands > and like them the ^ 

coat - go through a similar change 

during secretion, but they are more convoluted, and have 
longer ducts. 



INTESTINAL GLANDS. 



207 



The Glands of Peyer. — Those are found principally in 
the small intestine, and arc most numerous near the ileo- 
cecal valve. They are of two forms — single {glandula 
solitaries), sometimes called solitary glands, and in groups, 
called Peyer s 'patches. They are of oval form, about one-half 
inch in diameter, their longer axis longitudinal. 

In structure they consist of single or aggregated masses 
of adenoid tissue, forming lymph follicles. Each gland is 
fro m one twenty- 
fourth to one twelfth 
of an inch in diam- 
eter. The glands are 
most numerous 
in the submucous 
coat, but sometimes 
they project through 
the muscularis mu- 
cosa into the mucous 
membrane. In case 
of the agminate 
glands, each follicle 
reaches the free sur- 
face of the intestines, 
and is covered with 
columnar e p i - 




Fig. 117. — Vertical Section of a Villus. 
a. Striated basilar epithelium. 



b. Columnar 



rlir*linrn fYrko-ni-nrvo epithelium, c. Goblet cells, d. Central lymph 

milium, wpeillllgb vessel, e. Smooth muscular fiber (involuntary). 

r^-P +1^ m^,^~ „„„ /• Adenoid stroma of villus containing lymph 

01 tile crypts SUr- -corpuscles. (After Sanderson.) 

round each gland. 

Peyer's patches are most prominent and larger in children 
and young persons. 

The Villi. — These (Fig. 117) are found only in the 
mucous membrane of the small intestines. They are vas- 
cular, varying from one forty-eighth to one eighth of an inch 
in length, covering the mucous membrane, giving to it a vel- 
vety appearance. According to Krause, there are from fifty 
to ninety to the square line in the upper part of the intestines, 
and forty to seventy to the same area in the lower part. They 



208 



THE ALIMENTARY SYSTEM. 



vary in form, just as the lymphatics they receive are empty 
or full. 

Each villus consists of a small projection of mucous mem- 
brane, supported on its interior by fine adenoid tissue, form- 
ing a framework, or stroma, in which the other constituents 
are contained. 

The mucous membrane which covers the villus is made 
up of columnar epithelium, which rests on a fine basement 

membrane, be- 
neath which are 
blood vessels, 
fibers of the mus- 
cularis mucosae, a 
single lymphatic, 
or lacteal vessel, 
which is rarely 
looped or 
branched (Fig. 
118). The cells 
are arranged ra- 

Fig. 118. — Cross-Section of a Villus. diallv and con- 

1. Columnar epithelium. 2. Basement membrane. 3. . -' 

Central lacteal. 4. Blood capillary. 5. Goblet cell. 6. tain numerous 
Lymph corpuscles between epithelial cells. 7. Section 
of involuntary muscle fiber. 8. Adenoid tissue. goblet cells. 

The muscularis mucosae is arranged into a hollow cone imme- 
diately around the central lacteal, and is thus beneath the 
blood vessels, and by contraction aids in forcing the chyle 
into the lacteals. If the lacteals have valves, what would be 
the effects of the pressure from the contraction of the muscle 
fiber of the muscular layer around the lacteal ? These tubes 
make up the system vessels, called lacteals, and are but modi- 
fied lymphatic vessels, whose purpose is to absorb and carry 
the chyle to the thoracic duct. 

The Large Intestine. — This forms the remainder of the 
alimentary canal, is about five feet long, and varies in dia- 
meter from one and one-half to two and one-half inches. It 
consists of the following portions: The portion below the 
entrance of the small intestine, with its appendix (vermi- 




COLON AND SALIVARY GLANDS. 209 

form appendix), the coecum; the terminal portion, the rec- 
tum; the portion between these parts, the colon. 

The colon is the longest part. It begins on the right of 
the abdomen, extends upward (ascending colon), across 
(transverse colon), and then downward on the left side (de- 
scending colon), where it makes an S-shaped bend (sigmoid 
flexure), below which the rectum begins, completing the 
larger intestines. 

At the union of the large and small intestines is found a 
valve (ilio-co?cal), formed by two flaps of mucous membrane 
sloping downward into the colon, and so arranged as to per- 
mit bodies to pass readily from the ileum to the colon, but 
not in the other way. 

The mucous coat of the large intestine is like that of the 
small, except that the mucous membrane has no villi nor val- 
vule conniventes, nor Peyer's patches." 

It has follicles and glands much like those of the small 
intestines. 

The muscular coat consists of an external longitudinal 
and an internal circular layer. The former is partly col- 
lected into three flat longitudinal bands, between which the 
longitudinal layer, while present, is very thin, and being 
shorter than the walls to which they are attached, form sac- 
culi. The circular fibers form thin, continuous layers, being 
more numerous in the construction of the sacculi, and form 
in the rectum the internal sphincter. 

ACCESSORY ORGANS. 

The Salivary Glands. — There is need of other fluids in 
the process of digestion than those secreted by the alimen- 
tary canal. To supply this need, there are organs connect- 
ing with the alimentary canal, by which the needed, fluids are 
made. In general, their structure is that of a complex sys- 
tem of minute tubes lined with mucous membrane. 

Opening into the mouth are the salivary glands. There 
are three pairs of these organs: the parotid, situated just 
in front of the ears, its ducts (Stensons duct) opening inside 
14 



210 



THE ALIMENTARY SYSTEM. 



the cheek, opposite the second upper molar tooth; the sub- 
maxillary, between the two halves of the lower jaw, its duct 
(Wharton's duct) opening beneath the tongue; the sublingual 
(see Fig. 120), which lies beneath the mucous membrane of 
the floor of the mouth, close to the symphysis — its ducts are 
called ducts of Rivinus. 

There are three varieties of salivary glands, according 
to the nature of their secretion. 

I. True salivary glands, as the parotid, with small alve- 
olar lumen; the cells lining the tubule are short, granular, 
columnar cells. 

II. True mucus-secreting glands, as the sublingual, with 
larger tubules, and larger lumen, and larger lining cells. In 
these we find two kinds of cells — ( 1 ) mucous, or central 
cells, which are transparent columnar cells, having irregular 

or flattened nu- 
clei ; (2) cres- 
cents of Gian- 
uzzi — these are 
parietal cells of 
crescent shape, 
distributed a t 
intervals 
between the 
central cells of 
the basement 
membrane. 

III. Muco- 

salivary, or 

mixed glands, 

Fig. 119. -salivary Glands. as the submaxil- 

1. Parotid gland. 2. Submaxillary gland. 3. Labial l flrv w h l o li 
glands. 4. Duct of parotid gland. 5. Buccal glands. iai J? 

have part of the 
glands, like that of the mucous gland, and the rest like that 
of the salivary glands proper. 

The Liver. — The liver (Fig. 121) is the largest gland 
of the body. Its position is in the upper part of the abdomen, 




STRUCTURE OF THE LIVER. 



211 



more on the right than the left, just below the diaphragm. It 
is of a dark, reddish-brown color, and of soft, pliable texture. 

The ducts from each half of the liver unite to form he- 
patic ducts. These unite with the cystic duct, and the com- 
mon duct thus formed enters the duodenum about four inches 
from the pylorus. 

The liver is a highly vascular organ, and receives its blood 
supply from two distinct sources — (1) the hepatic artery; 
(2) the portal veins. The hepatic artery brings blood to the 
organ, which, together with the blood from the portal veins, 
is returned to the vena cava by the hepatic vein. 

The liver is covered incompletely by the peritoneum; 
beneath this covering, on the entire surface of the liver, is a 
very fine coat of connective tissue (areolar tissue). The con- 
nective tissue is the thickest where the peritoneum does not 
cover the liver, 
and invests the 
lobules w i t li a n 
almost impercep- 
tible layer of con- 
nective tissue. 
This tissue at the 
transverse fissure 
is merged into the 
connective tissue 
investment, called 
the capsule of 
Glisson, which in- 
vests the portal 
vein, hepatic ar- 
tery, and the he- 
patic duct as they 
enter the liver at 
this part, and accompanies them in their branches through 
the substance of the liver. 

The liver is made up of small roundish or oval portions, 
called lobules, which have a diameter of one twentieth to 




7 6 14 

Fig. 120. — Subungual Gland. 
1. Sublingual gland. 2. Glands of the top of the 
tongue. 3. Lingual nerve. 4. Hypoglossal nerve. 
5. Sublingual artery. 6. Duct of submaxillary gland 
7. Duct of sublingual gland. 8. Styloglossus muscle. 
9. Lingual. 10. Genio-glossus. 11. Hypoglossal. 
12. Cut end of hyoid bone. 13. Mylohyoid. 14. 
Genio-hyoid. 15. Gut end of inferior maxillary. 16. 
Genio-glossus. 17. Transverse ligament. 



212 



THE ALIMENTARY SYSTEM. 



one tenth of an inch, and are made up of minute branches, 
of the portal veins, hepatic artery, hepatic vein, and hepatic 

13 




Fig. 121. — The Liver. Seen from the Back and Lower Surfaces. 
1. Hepatic vein. 2. Vena cava inferior. 3. Hepatic vein. 4. Caudate lobe. 
5. Eight lobe. 6. Hepatic artery. 7. Hepatic duct. 8. Portal vein. 9. Gall cyst. 
10. Quadrate lobe. 11. Ligamentum teres. 12. Left lobe. 13. Ligamentum 
venosum. 



cells (Fig. 123). 




Fig, 122. — Lobule of Liver. 
1. Central vein. 2. Peripheral, or interlobular, 
veins. 



The cells become somewhat polyhedral 
in form from mu- 
tual pressure. 
They are from one 
one thousandth to 
one eight hun- 
dredth of an inch 
in diameter, hav- 
ing one or more 
prominent nuclei. 

In their cell 
substance are 
found numerous 
fatty molecules, 
possibly some 
granules o f bile 
pigment, and a vis- 




PLATE VIII. 

Fig. 71.— A Diagram Designed to Illustrate the Connections of 

the Motor and Sensory Conducting Tracts of the 

Cord with the Spinal Nerves. 

(Modified from Bramwell.) (From Ranney.) 

M. Motor fibers of the anterior root of a spinal nerve. S. S'. Sensory fibers 
of the posterior root. Note that the course of S and S' are not the same. Some 
sensory fibers pass directly through the posterior horn of the spinal gray sub- 
stance, and others through Burdach's column to reach the gray substance. The 
direct cerebellar column is composed of fibers which start in Clarke's column 
of cells. The fibers of the two pyramidal tracts become united to the motor 
cells in the anterior horns of the spinal gray substance. 



SECRETION OF THE BILE. 213 

ible amount of glycogen. They sometimes exhibit a slow 
amoeboid movement. They are supported by a very 
delicate tissue, continuous with the interlobular connective 
tissue. 

The arrangement of the blood vessels of the liver is very 
complex. The portal vein in its course gives off small 
branches, which divide and subdivide between the lobules, 
limiting them in forming the interlobular veins. From 
these interlobular veins is given off a dense capillary net- 
work, which is prolonged into the substance of the lobule, 
and these capillaries re-collect to form a vein in the center of 
the lobule, called the intralobular vein; the intercellular 
spaces give rise to the bile capillaries, which unite to form 
the hepatic ducts. 

The Secretion of the Bile. — The secretion of the bile is 
going on constantly, but is accelerated on taking food, and 
retarded during fasting. The 

bile is formed in the hepatic >/^©%@^c5^v 

cells, and discharged into the >/©^M^^S^^^pV 
minute hepatic ducts, and from Av^S^X^S^^j/^m 
these into the main hepatic H^Sr^&^rnfe Am^/M 
ducts, and may be carried at L-^^^^s^^T^^ZoTqh 
once into the duodenum. This Wv^-V/'SixJ^ 
probably only takes place dur- V^^ro^^^X^^W 
ing digestion; i. e., for three ^^^V®X^^^^^ 
to five hours after food is ^i^^Cj^^V^ 

taken. When it is not needed Fig. 123.— hepatic Cells. Liveb 

m j. ,. . of Cat. 

for digestion, it regurgitates (Brinckiey, c. w. b.) 

from the common bile duct, 

through the cystic duct, into the gall bladder, where it accum- 
ulates till it is needed for the next period of digestion, when 
it is discharged into the intestine. 

The intralobular veins discharge their contents into veins 
called sublobular veins (Fig. 122), which unite to form the 
main branches of the hepatic veins, which in turn leave the 
posterior border of the liver to form two or three principal 
trunks, which empty into the superior vena cava. The sub- 



214 



THE ALIMENTARY SYSTEM. 



lobular and hepatic veins haA^e little or no connective tissue 
around them, and their walls being very thin, form mere 
channels in the substance of the liver. The hepatic artery is 
distributed similar to that of the portal vein, its blood being 

returned by small 
branches either 
into the ramifica- 
tion of the portal 
veins or into the 
capillary plexus of 
the lobules which 





Fig. 125. — Opening op 
Duct from the Liver 

and the Pancreas. 

1. Hepatic duct. 2. 
Pancreatic duct. 

connect the inter- 
lobular and the in- 
tralobular veins. 
The chief function 
of the hepatic vein 
is to distribute 
blood for the nu- 
trition of the cap- 
sule of Glisson to 
the walls of the 
ducts and blood vessels, and to other parts of the liver. The 
hepatic duct has a distribution and division similar to that of 
the portal vein. It has its origin in the minute passages 
between the cells of the lobule, and forms bile capillaries. 



Fig. 124. — The Portal Circulation. 
1. Liver. 2. Gall cyst. 3. Posterior surface of 
stomach. 4. Pancreas. 5. Spleen. 6. Duodenum. 
7. Small intestine. 8. Caecum. 9. Ascending colon 
(right). 10. Descending colon (left). 11. Rectum. 
12. Left gastroepiloic vein. 13. Short gastric vein. 
14. Coronary vein. 15. Portal vein. 16. Right gastro- 
epiloic vein. 17. Splenic vein. 18. Inferior mesen- 
teric vein. 19. Left colic vein. 20. Superior hem- 
orrhoidal. 21. Right colic vein. 22. Superior mesen- 
teric vein. 



BILE AND PANCREATIC JUICES. 215 

Fat Digestion. — As has been stated, the purpose of diges- 
tion is to render the food soluble. Fats may be made soluble 
in two ways: (1) by making them into emulsion, (2) by 
converting them into soaps. 

The first of these processes is purely physical, simply 
being the division of the oil into microscopic drops ; and the 
smaller the drops the more complete the emulsion. 

The emulsion is formed more readily when the fats are 
old, and contain a free acid, and in the presence of an alkali. 
Milk is an example of an emulsion. 

The second process is a chemical one. Most of the com- 
mon fats are produced by treating glycerin with an acid 
(called fat acids), as palmitic acid,, stearitic acid, oleic acid. 

Glycerin + Palmitic Acid = Palmitin (fat) + water. 

Glycerin + Stearitic Acid = Stearin (fat) + water. 

Glycerin -f Oleic Acid = Olein (fat) + water. 

Glycerin belongs to a class of bodies called alcohols, which 
in the presence of acid act as bases, producing salts, so that 
fats are called salts {ethereal salts). 

A can of nitroglycerin and a can of lard are closely 
related. 

Glycerin + Xitric Acid = Xitroglycerin + water. 

Glycerin + Palmitic Acid = Palmitin + water. 

When a fat is treated with an alkali, the metal of the 
alkali displaces the glycerin radical, and gives a metal salt of 
the acid and glycerin. The salt produced by the alkali join- 
ing with the fat acid is called a soap, and the process by which 
the fat is decomposed is called saponification. 

Palmitin + Alkali (Caustic Soda) = Soap (Sodium Pal- 
mate) + Glycerin. 

Palmitin + Alkali (Caustic Potash) = Soap (Potassium 
Palmate) + Glycerin. 

Sodium alkalies give hard soaps ; potash alkalies give soft 
soaps. 

We can now see a reason for the alkaline nature of the 
bile and pancreatic juices; but as the alkaline nature of the 
intestinal juices is not very great, so there is only a small 



216 



THE ALIMENTARY SYSTEM. 



part of the fats converted into soaps, and it is now thought 
the function of these is to assist in the emulsification of the 
fats. 

The Gall Bladder. — This is a pear-shaped bag (Fig. 
124), situated under the right lobe of the liver, with its 
larger end projecting beyond the front margin of the liver, 

3 




Fig. 126.— The Pancreas and Spleen. 
1. Vena cava. 2. Esophagus. 3. Spleen. 4. Pancreas. 5. Duodenum. 6. 
Superior mesenteric vein. 7. Small intestine. 8. Transverse colon. 9. Kight 
Kidney. 10. Dotted line shows outline of the liver. 11. Deep black line gives 
outline of the stomach. 

and its smaller portion contracting into the cystic duct. It 
lies below the peritoneum, by which it is supported. It is 
about four inches long, and one inch broad at its widest part. 
It has three principal coats : an external, serous ; a middle, 
fibrous (areolar), containing plain muscular fibers; and 



GLANDS. 217 

internal, mucous, with columnar epithelium. To the naked 
eye the mucous membrane presents the appearance of honey- 
comb. The mucous membrane of the duct is raised up in 
crescent folds, which together appear like a spiral valve, and 
aid in the retention of the bile during the interval of diges- 
tion. The mucous glands of the body of the organ and ducts 
secrete a viscid mucus. 

The Pancreas. — This organ (Fig. 126) lies transversely 
across the abdominal cavity, opposite the first lumbar ver- 
tebra, back of the stomach. It is elongated, somewhat tri- 
angular in form, the larger end being embraced by the curve 
of the duodenum. It is of pinkish color, soft texture, and 
in general structure like the salivary glands. It is invested 
by a thin connective tissue capsule, which sends off divisions, 
or septa, between the lobules, along which the nerves and 
blood vessels find their way to the substance of the gland. 
The main duct begins at the narrow end by the union of the 
ducts from the lobules of this part, and, running the whole 
length of the gland, receives in its course contributing ducts 
from the lobules, the ducts joining the main one at nearly 
right angles. Its duct (canal of Wirsung) enters the duo- 
denum obliquely, forming, with the bile duct (ductus com- 
munis choledoclius) , a common duct. While the ducts seem 
to unite, their union is not complete, as they do not mingle 
their contents until after they enter the wall of the duo- 
denum, the ducts being separated by a septum (Fig. 125). 

The gland is of the compound racemose variety, but its 
acini are more tubular and numerous than the salivary glands. 
It is about six inches long, one and a half inches wide, and 
one inch thick. 

THE SPLEEN. 

The spleen (Fig. 126) is situated to the left of the 
stomach, between it and the diaphragm ; is of deep red color, 
of variable shape and size, being generally oval, somewhat 
concavo-convex. It is the largest of the so-called vascular 
organs. Its vessels enter and leave the gland at the inner 
side of hilus. 



218 THE ALIMENTARY SYSTEM. 

Structure. — It is almost entirely covered by a serous coat, 
derived from the peritoneum. It has beneath this coat a 
covering of connective tissue, which forms its true capsule, 
and which sends off prolongation trabecules into the substance 
of the organ, which branch and anastomose to form a sup- 
porting framework, or stroma, and in the meshes of which is 
held the proper substance, the spleen (spleen-pulp). In the 
capsule, the proportion of elastic fibers predominate, and 
mingle with the unstriated muscuLar tissue. These elements 
enter into the make-up of the trabecular It has a large 
supply of blood vessels. 

Functions. — Its more important functions are: (1) To 
store up some of the changed and absorbed proteid food, that 
it may be gradually introduced into the blood, as demanded 
by the general system. This is supported by the fact that 
the spleen gradually increases in size during the digestive 
process, and from the larger amount of fine granular albu- 
minous plasma in its parenchyma; (2) to form white cor- 
puscles; (3) to form red corpuscles. This is probably only 
true during the very early stages of the animal life. It may 
have a part in this work from its connection with the influence 
it has upon the red marrow. It was formerly thought that 
the spleen destroyed the worn-out red corpuscles. This theory 
has been practically abandoned; (4) that it has a special 
nitrogenous metabolism to perform is quite well established. 
The very large amount of uric acid, xanthin, and leucin favor 
this idea; (5) that it has an influence over the portal circu- 
lation. This function is looked upon as subordinate. 

FLUIDS OF DIGESTION". 

Various fluids have been mentioned, as the saliva, the 
mucus, the gastric juice, pancreatic juice, and intestinal 
juice. Where and how are these fluids made? 

They are produced by the mucous membrane and by the 
various glands by a process called secretion. This is accom- 
plished by the activity of the cells which line the glands, 
also by those of the mucous membrane. In this little labo- 
ratory, the cell, are made these strange compounds, The 



FLUIDS OF DIGESTION. 219 

process is a very complex one. It is not a process of sifting 
by which certain substances contained in the blood are taken 
out, for the products of secretion are very different from 
anything found in the blood. Again, secretion will go on 
in the absence of a blood supply. These are products manu- 
factured by the cell by its peculiar and individual activity. 
This is normally accomplished in the following manner : — 

1. An increased flow of blood is produced by the dilation 
of the small arteries (caused by a very beautiful arrangement 
of the nerves and the muscular fibers of the arteries, which 
will be explained w T hen we consider blood circulation). 
There is a rise in the temperature of the gland, and a deep- 
ening of the color of the mucous membrane. 

2. By a nervous stimulus to the cell, caused by the 
reflex influence of the medulla. Most of the glands, and 
probably all, receive the reflex nervous stimulus. 

3. By the activity of the cell, which manufactures from 
its substance the secreting product, which it expels into the 
adjoining cavity. If the cells of the salivary glands be ex- 
amined between the acts of active secretions, they appear 
very granular, hiding the nucleus, the lines between the cells 
being not easily made out and with a clear band at their 
outer margin. If, however, they should be examined at the 
time of the active secretion, a marked difference is noticed. 
The outline of the cell becomes more clearly marked, the 
nucleus prominent, the clear space large, and the entire cell 
less granular. 

It would seem, then, that in those glands which are inter- 
mittent in their action, that secretion consists of two acts: 
(1) A passive one, in which it makes from its protoplasm the 
secreting product which appears as granules (or at least the 
secreting factors), and (2) the act by which these products 
are expelled from the cell into the tubules of the glands. 

In those glands in which the secretion is constant, as in 
the liver, these acts take place simultaneously. 

The saliva, the gastric juice, and the pancreatic juice are 
intermittent; the bile, constant. 



220 THE ALIMENTARY SYSTEM. 

The digestive fluids consist of a large portion of water, 
and an alkaline (or acid principle), and some organic fer- 
ment, the active principle in the digestion. 

Mucus. — This is the fluid secreted by the general surface 
of the mucous membrane and by the mucous glands. It is 
slightly alkaline, viscid in consistency, contains a large pro- 
portion of water and a ferment called mucin. It has the 
following functions : — 

1. In general, to moisten the mucous membrane. 

2. By viscidity to aid in deglutition. 

3. In digestion, especially in the stomach, to change cane 
sugar to grape sugar. 

Saliva. — The saliva, as found in the mouth, is the mix- 
ture of fluids from the parotid, sublingual, submaxillary, and 
buccal glands. We can here speak only of the saliva as a 
mixed fluid. In consistency it is less viscid than mucus, con- 
tains a large proportion of water, is alkaline in reaction, its 
ferment being ptyalin. Its functions may be enumerated 
as follows : — 

1. Generally and probably its chief function is to mois- 
ten the food, and aid in the formation of the bolus. 

2. To dissolve substances soluble in water, and by its 
alkaline reaction to render many substances soluble which 
would not dissolve in water. 

3. To aid in the articulation of speech. 

4. According to Liebig, to carry down into the stomach 
small quantities of oxygen. 

5. To change starch to maltose and other forms of sugar. 

6. It is necessary to the sense of taste to dissolve sapid 
substances. 

7. It has no digestive action upon the proteids and fats. 

8. By alkaline nature, it acts as a stimulant to the gas- 
tric glands. 

Gastric Juice. — As will be remembered, this is the secre- 
tion of the gastric follicles of the stomach. It has a large 
proportion of water, a small per cent of acid (hydrochloric), 
and a ferment called pepsin and rennin. The functions of 
this fluid are : — 



FLUIDS OF DIGESTION. 221 

1. To digest a class of bodies called proteids, of which 
we shall learn more when we study the subject of food. 

2. To disintegrate the food by its solvent action on con- 
nective tissue. 

3. To antisepticize the food. 

4. By acid nature to act as a stimulus to the flow of the 
alkaline secretions of the intestine, liver, and pancreas. 

The proteids of the food are insoluble, and do not readily 
pass through membrane by osmosis. The part of the work 
of the stomach digestion is to change these into the peptones, 
which renders them soluble. This is accomplished by the 
action of pepsin in the presence of an acid medium (hydro- 
chloric). 

If the gastric juice be neutralized by an alkali, the pepsin 
does not exercise its digestive power on proteids. 

In the digestion in the small intestines there are three 
fluids that take a part in the action : the bile, pancreatic, and 
intestinal juices. 

The Bile. — In composition the bile contains a large pro- 
portion of water, bile salts, and bile pigments, but no pro- 
teids or ferments. 

The bile salts are sometimes called bilin, and consist of 
sodium glycocolate and sodium taurocolate. In the human 
bile the sodium gylcocolate is in excess (4.8 to 1.5). The 
bile also contains cholestrine (an alcohol) and a small per 
cent of mineral salts. The color in carnivora, omnivora, and 
man is a bright, golden red. 

While there have been many conflicting views in regard 
to the function of the bile, experiments seem to establish the 
following uses : — 

1. To aid the pancreatic juice in emulsifying fats and 
oils. It also has, to some degree, the power of saponification. 

2. To neutralize the acid of the gastric juice. 

3. To awaken the secretion of the intestinal juice. 

4. To aid in the osmosis of tbe fats, by moistening the 
mucous membrane of the intestines. 

5. To prevent putrefaction, by its antiseptic properties. 

6. To act as an excrementitious fluid; i. e., takes from 



222 THE ALIMENTARY SYSTEM. 

the blood certain injurious principles, that they may be 
thrown from the system with the refuse of digestion. 

7. To act as a stimulant to the muscular coats of the in- 
testines. 

Glycogen. — This is a carbohydrate substance found in 
the liver. It has a formula (C 6 H 1 O g ) like that of starch, 
and, like starch, it is converted into sugar by hydration, but 
it differs from starch in that it gives a wine color with iodine. 
The source of the glycogen is, without doubt, the food, as 
there is little or no glycogen in the liver of a starved animal. 
Its great source is the carbohydrates, as is shown by the fact 
that when animals are fed on diet of this kind, there is an 
increase of glycogen. It is also derived from proteid ma- 
terial. During digestion, especially after a meal rich in 
carbohydrates, the blood going to the liver through the portal 
vein contains more sugar than the blood leaving the liver by 
the hepatic vein. During the interval of digestion, however, 
the hepatic venous blood contains about twice, as much as the 
portal venous blood. From this it would seem that the liver 
regulates the amount of sugar in the blood, storing it as gly- 
cogen during digestion, and reconverting this glycogen into 
sugar to be given to the system as its needs demand. 

The destination of the glycogen of the liver is, however, 
to some extent, under discussion. The burden of the evidence 
seems to favor the view given above, that it is converted into 
sugar, and undergoes combustion in the tissues. Heavy mus- 
cular work leads to the disappearance of hepatic glycogen; 
the amount of sugar in the venous blood of an active muscle 
is slightly less than in arterial blood. The sugar cycle of a 
well-fed animal is as follows: The sugar absorbed from the 
alimentary canal enters the portal blood, is in great part 
stored as glycogen in the liver cells, is gradually reconverted 
into sugar, w T hich passes by the hepatic veins, is consumed by 
living muscle, and discharged as carbon dioxide (C0 2 ) and 
water (II 2 0). 

Glycogen is also found in muscle tissue, especially in 
skeletal muscle, where it probably forms a local reserve for 



FLUIDS OF DIGESTION. 223 

muscular energy. By some glycogen is thought to be also a 
source of heat. 

Pancreatic Juice. — This is a clear, viscid fluid, having a 
decidedly alkaline reaction with some proteids and organic 
ferments. 

The ferments of the pancreatic juice are trypsin, amylop- 
sin, stcapsin, and a special milk-curdling ferment. Trypsin 
has the power of converting the proteids into peptones. It 
acts best in an alkaline medium, and is more powerful than 
pepsin in its action on both proteids and gelatins. 

Amylopsin has the power of converting starch into mal- 
tose, which is converted into dextrose before absorption. 
Amylopsin cannot be distinguished from the ptyalin of the 
saliva. The milk-curdling ferment (rennet) is very power- 
ful ; one c.c. of brine extract will coagulate fifty c.c. of milk 
in a little over a minute. 

The power of the pancreatic juice to emulsify and sapon- 
ify the fats and oils is thought to be due to steapsin. 

In its action pancreatic juice closely resembles the saliva, 
but has a much stronger action upon starch. It has the fol- 
lowing functions : — 

1. Acts with great energy upon raw or boiled starch, con- 
verting it into grape sugar. 

2. Exercises an action upon proteids similar to that of 
gastric digestion. The following differences are to bo 
noticed : — 

a. In gastric digestion the fibrin becomes swollen and 
translucent, while in pancreatic it remains opaque, and seems 
to have suffered corrosion rather than solution. 

b. The product of gastric digestion is acid albumin, while 
that of pancreatic is alkaline albumin. 

c. The greatest difference in the production of two nitrog- 
enous substances, leucin and tyrosin. 

3. Its action upon fats is twofold. 

a. It emulsifies fats. 

b. It breaks up the fat into glycerin and the fatty acid, 
and if an alkali is present, saponification takes place. 



224 THE ALIMENTARY SYSTEM. 

Intestinal Juice. — This fluid is supposed to be a secre- 
tion of the crypts of Lieberkiihn. Evidence is wanting as to 
its part in digestion ; probably it has no direct action upon 
either fats or proteids. In some animals it has the power of 
changing starch into grape sugar; by fermentation action to 
convert cane sugar into lactic acid, and this into butyric, with 
the evolution of carbon-dioxide and free hydrogen. 

By most physiologists its action is not considered very 
important. 

ALIMENTATION. EXPERIMENTS. 

Prepare some arrowroot (which is almost pure starch), 
and make a thin paste with boiling water. Let it cool. Try 
the following : — 

1. Add two or three drops to a test tube half full of water. 
Then add a few drops of a solution of caustic potash ; to this 
add a few drops of a solution of blue vitriol (copper sul- 
phate). Mix thoroughly, and boil for a short time over a 
spirit lamp. 

2. After thoroughly rinsing the mouth, collect some of 
the saliva in a clean test tube. Dilute with water. Add the 
caustic potash and the vitriol as before, and boil. What 
change in color do you note ? Is there any sugar (maltose) 
in the solution ? How do you know there is not ? 

3. Take three or four drops of the paste and 10 c.c. of 
saliva, and mix them in a tube about half full of water. 
Place the tube in a warm place (about 40° C), and let it 
stand for five or ten minutes. Then add the caustic potash 
and the vitriol solution as before. Is there any change ? 
What does it show? What is the source of the sugar 
(maltose) ? 

4. Take a solution (the same, 3), and add a few drops of 
vinegar, or acetic acid, and proceed as in 3. What change 
do you note? 

5. Take 10 c.c. of saliva in a test tube, and add two grains 
of raw starch. Add the same amount of starch to enough 
water to make a paste, and boil in a test tube, and when the 
paste is formed, let it cool. When cool, add 10 c.c. of saliva ; 
set it and solution of raw starch aside under the same con- 
dition. After standing for twenty minutes, test each for 
maltose by adding to each 5 c.c. of Fehling's solution. In 



EXPERIMENTS, 



225 



which do you get the larger precipitate? What does this 
show ? How do you account for the difference ? 

Gastric Digestion. — 1. Obtain a pig's stomach. Cut it 
open, and wash away its contents with a gentle stream of 
water. Xow carefully dissect off the mucous membrane from 
its middle part; cut in very fine pieces, and put aside for 
two or three days in three or four ounces of glycerin. The 
glycerin will dissolve the pepsin. Now strain off the glycerin 
through muslin. 

2. Secure from the butcher some whipped blood. Wash 
it thoroughly with water. Put aside in fifty-per-cent alcohol. 

3. Add sixty drops, or 4 c.c, muriatic acid (hydrochloric 
acid) to a pint of water. 

4. Dilute a teaspoonful of the pepsin solution of Experi- 
ment 1 with two tablespoonfuls of water. Put the mixture 
into a test tube, and set aside in a warm place for twenty-four 
hours after adding a small portion of the fibrin solution. 
Does any change take place? Avoid too high a heat (not 
over 42° C), as the mixture should not be hot. What facts 
do the results show ? Test for peptones. 

5. Put some of the solution of Experiment 3 in a test 
tube, and add some of the fibrin, and put away in a warm 
place for twenty-four hours. What change do you notice? 
What does this show ? 

6. Fill a clean test tube half full of the mixture of Ex- 
periment 3. Add a teaspoonful of solution of Experiment 
1, then add some of the fibrin. Place in a warm place for 
twenty-four hours. What change takes place ? What does 
it show ? 

7. Proceed as in Experiment 6, but add some seventy or 
eighty per cent of alcohol. What effect has it upon the action 
of the muriatic acid and pepsin ? What does it teach as to 
the effect of alcohol on digestion ? 

8. Action of Bile on Fatty Substances. — (a) Shake up 
some olive oil with water in a test tube. Do the liquids sep- 
arate when ycu cease to shake them? (b) Secure some ox- 
gall. Xow shake up some oil with the bile instead of water. 
What difference do you note ? 

9. To Make Pancreatic Solution. — Secure from the 
butcher the pancreas of the pig. Keep it moistened with 
water for a day; and after mincing well, add eight or ten 
times its own weight of glycerin. Set the mixture aside for 

15 



226 THE ALIMENTARY SYSTEM. 

three or four days, occasionally stirring it. The glycerin 
will dissolve out the pancreatin. Strain through muslin. 

10. To 10 c.c. of a one-per-cent solution of carbonate of 
soda add 1 c.c. of pancreatin. Add to this a small amount 
of starch paste, and set aside in a warm place where it 
will not be over 42° C. Examine after twenty-four hours, 
and test for sugar. 

Take a similar solution, but add to it hydrochloric acid 
until the solution is acid; proceed as in Experiment 10. 
What change do you note ? If the contents of the small 
intestines were acid, what effect would it have upon diges- 
tion ? 

11. To 5 c.c. of the solution of pancreatin add 10 c.c. of 
a two-per-cent solution of bicarbonate of soda. To this solu- 
tion add ten or twelve drops of olive oil or a small amount 
of butter. Keep the mixture near 40° C. After four or 
five hours, what change do you note? Kepeat the experi- 
ment, but omit the bicarbonate solution. Do you note any 
change ? Examine a drop, in each case under high power. 
In either case is the resulting solution soluble in water ? 

12. Make a solution as in Experiment 7, but instead of 
starch take a small amount of the white of an egg. Try the 
experiment also with some cooked egg. 

13. In a similar way try some meat. 

14. Try the action of pancreatin on milk. 

15. Make careful measurements of the circumferences 
of an egg. Soak the egg in a dilute solution of hydrochloric 
acid (three parts acid to one hundred parts water) until 
the mineral matter is removed, which may be told by the 
covering being soft and pliable. Make a strong solution of 
grape sugar (ten grams sugar to one hundred c.c. of water). 
Test five c.c. of the solution to determine how many cubic 
centimeters of the Eehling's solution it will precipitate. 
Place the egg in one hundred c.c. of the grape sugar solu- 
tion, and leave it in the solution for several hours. Examine 
it from time to time to note any changes. Make a careful 
measurement of the circumferences of the egg after it has 
been in the solution. Has there been any increase in the 
size of the egg ? How do you account for the change ? Test 
the solution in which the egg has been soaking? Has 
there been any loss of the amount of sugar in the solution ? 
Test five c.c, as above. How does the amount of Eehl- 



EXPERIMENTS. 227 

ing's solution precipitated compare with the test first 
made 3 Carefully break the egg, and test it for grape 
sugar 1 How do you account for the presence of the sugar 
in the egg ? 

16. Prepare an egg as in Experiment 15, and, after 
making the same measurements, place in a strong solution of 
pure cane sugar (ten grams to one hundred c.c. of water). 
Test ten c.c. with Eehling's solution. Do you get a precip- 
itate ? Test another five c.c, first boiling with one c.c. of 
hydrochloric acid for a few minutes, and let cool. Add 
Fehling's solution. What change do you note ? After the 
egg has been in the solution for twenty-four hours, test as in 
Experiment 15, but before adding the Fehling's solution, 
warm the solution with hydrochloric acid. What differences 
do you note ? Does as much of the sugar pass into the 
egg as in Experiment 15 ? 

IT. Prepare an egg as in Experiment 15, and place in 
pure water for twenty-four hours. Is there any change 
in the size of the egg^. Test the water for chlorides (see 
Appendix). Hoav do you account for their presence in the 
water ? 

18. Take an egg as prepared in Experiment 15, and keep 
it in fifteen-per-cent salt solution for twenty-four hours. 
What change do you note in the size of the egg? What 
reasons can you give for the change ? 

19. Repeat the experiment, using a normal salt solution 
(.6 per cent). Is there any change in the size of the egg^. 
What principles have you learned that govern the inter- 
change of liquids (osmosis) when separated by a membrane? 

20. Take fifteen or sixteen inches of the intestine of a 
rabbit ; clean, wash, and inflate. Tie at intervals of four or 
five inches; let dry. When dry, cut midway between the 
tied points, thus making that into little sacks, and suspend 
them in convenient-sized vessels containing water. In the 
first, place a grape sugar solution ; in the second, oil ; in the 
third, oil with an alkali (carbonate of soda) ; in the fourth, 
milk ; in the fifth, milk with a strong solution of pancreatin. 
Test the liquids in the respective vessels for sugar, oil, pep- 
tones. In which vessels has the substance in the sack passed 
through the wall of the sack into the liquid surrounding it ? 
Which of the substances passed most readily through the 
membrane into the water ? 



228 THE ALIMENTARY SYSTEM. 

DIGESTION. TEXT. 

Mastication. — This in man consists chiefly of an up-and- 
down movement of the lower jaw, combining the grinding 
action of the molar teeth with a certain amount of lateral 
and fore-and-aft movement. 

The principal muscles (Figs. 37 and 38) concerned in 
these movements are the temporal masseter, internal and 
external pterygoids, digastric, and buccinator. 

They receive their motor fibers from the fifth cranial 
nerve. During mastication the food is moved to and fro, 
and rolled about by the movement of the tongue, governed 
by the hypoglossal nerve. During this process there is a 
copious flow of saliva. 

Deglutition. — When sufficiently masticated, the food is 
gathered up into a bolus on the middle of the upper surface 
of the tongue. 

The front of the tongue being raised, the bolus is thrust 
back between the tongue and palate through the fauces. Just 
before its arrival there the soft palate is raised. By this and 
other movements the entrance to the posterior nares is blocked, 
while the soft palate is formed into a sloping roof, thus guid- 
ing the bolus down the pharynx. By the contraction of 
some of the muscles of the pharynx {stylo and potato pharyn- 
geus) the funnel-shaped bag of the pharynx is brought up 
to meet the descending morsel very much as a glove may be 
drawn up to meet the finger. The thyroid cartilage is now 
raised by action of the laryngeal muscles, and thus it assists 
the epiglottis to cover the glottis. 

The entrance to the nares and to the glottis being 
guarded, the impulse given to the bolus can have no other 
effect than to propel it beneath the sloping soft palate over 
the incline formed by the root of the tongue and epiglottis. 
When the bolus is large, it is received by the middle and lower 
constrictors of the pharynx, which, by their contraction one 
after the other from above downward, force it into the 
esophagus. 

By a series of successive contractions of the circular fibers 



DIGESTION. 229 

of the muscular coats of the esophagus it is forced downward 
by a creeping-like movement. When the morsel is small, or 
when a fluid is swallowed, the movement given to it by the 
tongue is sufficient to force it into the esophagus without 
the aid of the constrictors. In the act of deglutition we 
may note the following stages : — 

1. The thrusting of food through the isthmus of the 
fauces. This may be of long or short duration. 

2. The passage through the upper part of the pharynx. 
Here the food traverses a region common both to the food 
and respiration, and, in consequence of this, the movement 
here is as rapid as possible. 

3. The descent through the grasp of the constrictors. 
The food having passed the respiratory orifice, the passage 
becomes slower, with the exception of small morsels and 
fluids. 

4. The passage along the esophagus may be considered 
as the last stage, but it is in reality the beginning of the 
peristaltic movements common to esophagus, stomach, and 
intestines. 

The first stage of deglutition is voluntary. The second, 
taken as a whole, may be considered as reflex, although the 
earlier movements of this stage may be considered on the 
border land of voluntary and reflex action, and the third is 
without doubt reflex. The more recent observations war- 
rant the conclusion that, taken as a whole, deglutition is 
reflex, and its center of action is the medulla. 

Movements of the Stomach.— The object of the movements 
of the esophagus is to carry the food as rapidly as possible 
to the stomach, 1 and that of the intestines to carry the intes- 
tinal contents onward through the twisted course of the 



i A careful examination of the structure as far as the muscles are concerned 
shows they may be divided into two portions, the cardiac portion, made of 
weaker muscles (the/undus), and the pyloric, made of stronger developed muscles 
(the antrum). The pressure produced by the muscles of the antrum is over 
three times as great as that of the fundus. 

" The movements of the fundus serve to mix the food with gastric juice; the 
movements of the antrum serve to empty the contents of the stomach into the 
duodenum." — Schenck and Qilrhtr. 



230 THE ALIMENTARY SYSTEM. 

looped path, and the exposure insuring the thorough mixing 
of its contents and exposure to the surface of the mucous 
membrane for absorption. 

The movements of the stomach, however, have different 
purposes : — 

1. To provide an adequate exposure of the contents of 
the dilated chamber to the influence of the gastric juice. 

2. To propel the partially digested food, when ready, 
into the duodenum. We may therefore distinguish between 
the churning and the propulsive movements. 

When the stomach is empty, all the muscular fibers 
fall into what may be called an obscure tonic contraction. 
The whole stomach is small and contracted, and its cavity 
nearly obliterated, and from the greater number of circular 
fibers, its mucous membrane is thrown into longitudinal folds. 
As the food enters, the muscular fibers become relaxed with 
the exception of the pyloric sphincter, which remains at first 
permanently closed, and the less marked cardiac sphincter, 
which merely relaxes from time to time at each act of 
swallowing. As soon as the coats become relaxed, they set 
up an obscure rhythmical peristaltic contraction, giving rise 
to the churning movements. These movements are feeble 
at first, but become more pronounced as digestion proceeds. 
Before digestion proceeds very far, the propulsive move- 
ments begin. These occur at intervals, at first slowly, but 
afterward more rapidly. 

Movements of the Small Intestines. — As soon as the 
products from the stomach enter the small intestines, there 
begins a contraction of the circular muscular coats, giving 
an onward propulsive movement from above downward, 
caused by the lessening of the caliber of the intestine by 
the contraction of the circular fibers. Beginning at the 
pylorus, this movement may be traced the entire distance. 
The contraction of the longitudinal fibers may aid in the 
propulsive movement by alternating in their contraction with 
the circular fibers. They also aid the intestines to regain 
their caliber after contraction. 



DIGESTION. 231 

Movements of the Large Intestines. — They are similar in 
most respects to those of the small intestine, but less com- 
inieated and vigorous. 

DIGESTION. CHANGES WHICH THE FOOD UNDEEGOES. 

The following are some of the more important changes : — 

1 . The Mouth. — a. The food is divided, moistened, 
formed into a bolus, and prepared for swallowing. 

b. Some of the starch is acted upon by the saliva, and 
changed to maltose. 1 If the starch has been cooked, a much 
larger proportion is changed than when uncooked. Why ? 
(See Experiment 5.) 

2. The Stomach. — a. The action of the saliva upon the 
starch is arrested. 

b. The gross effect is to break up and partly dissolve 
the larger lumps of masticated food into a thick, grayish 
soup-like chyme, with which are still mixed variable quan- 
tities of larger and smaller masses of less changed food. 

In meat, by the solution of the connective tissue binding 
them together, the muscular fibers fall apart, and they are 
ultimately reduced partly to granular mass and partly to 
actual solution. 

The fats have the connective tissue binding the cell to- 
gether and the envelopes of the fat cells dissolved and the 
fat set free. 

In vegetable substances the proteid elements are in part 
dissolved, and although there is no evidence that in man the 
cellulose is dissolved in the stomach, the whole tissue is 
softened, and to a certain extent disintegrated. 

The chyme in general as it passes into the duodenum 
consists of : — 



iThe common statement that starch Is converted into grape sugar (glucose) 
by the action of saliva and pancreatic juice is not true. While the substance 
resulting from this action reduces Fehling's solution, it is quite different in its 
composition, and is called maltose, or malt sugar. The change which takes 
place in the digestion of starch is not a simple one, as commonly described, but 
is very complex, in fact, too complex to be described here. It should be stated, 
however, that there is a small amount of glucose formed by it that results from 
a secondary action, and not from the action of the ptyalin on the starch. It is 
formed from the maltose. 



232 THE ALIMENTARY SYSTEM. 

1. Starch unchanged by the saliva. 

2. Oils and fats set free in the gastric digestion. 

3. Dissolved proteids. 

4. Undissolved proteids. 

5. Debris of indigestible materials, as cellulose, etc. 
Eecent experiments seem to show that the amount of 

material actually dissolved in most specimens of chyme is 
very small. It is further shown that the action in the 
stomach is more one of preparation to digestion than of 
completed digestion; i. e., the great purpose 1 of gastric 
digestion is to reduce by disintegration the lumps of food 
to a more uniform mass, and thus facilitate the changes which 
are to take place in the small intestines. During the process, 
however, some of the material is converted into peptone, 
and the peptone thus formed is in part absorbed at once, 
but the greater part of the proteids remains unchanged, at 
least they are not converted into peptone. There is little 
or no change produced upon starches and fats. 

Sudden mental excitement may delay gastric digestion; 
also feeble and imperfect digestion may arise from purely 
nervous influences. An excessive formation of acid may be 
due to nervous disturbances. Anger and surprise often de- 
stroy the appetite and arrest digestion. 

3. In the Small Intestine. — ■ The semi-digested acid food 
from the stomach as it passes over the biliary duct causes 
a flow of bile and pancreatic juices which tend to neutralize 
the acid chyme, but the contents of the duodenum do not 
become distinctly alkaline until they have proceeded some 
distance beyond the pylorus. 

By intestinal digestion the following results are se- 
cured : — 

1. The change of starch into sugar is resumed. 

2. Proteids are largely dissolved, probably by action of 



i Stomach digestion has another very important function, that of thoroughly 
disinfecting the food. This is accomplished by the free hydrochloric acid, and 
also by the acid compounds it forms in digestion. This explains why a person 
may drink infected water during the digestion of a meal, which, if taken between 
meals, might prove fatal. 



DIGESTION. 233 

the bile and pancreatic juice, and to some extent possibly 
by the intestinal juices, assisted by various micro-organisms. 

3. Starch converted into sugar, and possibly the sugar 
is in part converted into lactic and other acids. 

4. Fats are largely emulsified and to some extent sapon- 
ified. 

5. By the time the food has reached the ileocecal valve 
it has been deprived of most of its nutritious properties, 
but by no means all. 

6. Such is the relation of water secreted in the intestine 
to that of the fluids absorbed, that the intestinal contents at 
the end of the ileum are about as fluid as in the duodenum. 

4. In the Large Intestine. — Among the more important 
changes the following may be noticed : — 

1. The contents become distinctly acid. That is not 
due, however, to the secretion of the intestinal walls, but 
to the acid fermentation which takes place in the contents 
of the intestines. 

2. Of the changes which take place we have no definite 
knowledge. It is probable that digestion of cellulose takes 
place here. 

3. Absorption is very active, and the contents soon lose 
their fluid consistency. 

Absorption. — The digested food must pass from the ali- 
mentary canal into the blood so that it may get to the tis- 
sues. The process by which it is accomplished is called 
absorption. The great absorbent vessels are the veins and 
lacteals, but in the process of absorption the veins perform 
the greater part. 

All along the course of the alimentary canal the mucous 
membrane is closely packed with blood vessels and lymphat- 
ics, so that as soon as any soluble substances are formed, 
they may be absorbed. The time of the passage of the 
food from the mouth to the stomach is so short that little 
absorption takes place before the food reaches the stomach. 
But while absorption takes place actively in the stomach, the 
intestines are the part most concerned in- this process. 



234 THE ALIMENTARY SYSTEM. 

It will be remembered that the villi are minute tubules 
projecting into the intestinal contents like the minute root- 
lets of the plants into the soil; that it is covered with a 
layer of cells resting on a fine reticulum; that it contains 
a network of capillaries and lacteal axes and lymph spaces 
(Figs. 117 and 118). In order, then, for the food to enter 
the blood or the lymph it must pass through the cells and re- 
ticulum of the villus and the cell layer of the capillaries. 
In absorption we may, therefore, distinguish two stages : — 

1. The passage through the epithelial cell of the walls 
of the villus and through the reticulum. 

2. The passage through the epithelial cell of the cap- 
illaries or the lymphatic radical. 

Experiments indicate that the first stage is something 
more than diffusion, or osmosis. It is accomplished by the 
activity of the epithelial cells, and it is, in one sense of the 
term, a vital process; for in case of fats, repeated observa- 
tions have shown that the neutral fats enter the cell sub- 
stance, and also that peptones are changed in their passage 
through the cell substance. 

The passage of the food materials through the walls of 
the villus is something more than osmosis; it is a process 
in which the activity of the cell plays an essential part. The 
passage through the cell walls of the capillary is more of the 
nature of osmosis, but that the tissues are living must not be 
lost sight of. 

The greater part of the peptone is absorbed by the veins, 
while the fats are almost entirely absorbed by the lacteals. 
The contraction of the villus and the presence of valves in 
the lacteals aid in the passage of the fats through them. 

When we study circulation, we shall then trace the 
course food takes after it is absorbed. 

How the Pood Gets to the Tissue. — By the act of ab- 
sorption the food material enters two streams, (1) the blood, 
and (2) the lymph. 

By the absorption of the food in the stomach the digested 
proteids ? soluble substances, and water leave the stomach 



EFFECT OF ALCOHOL ON THE DIGESTIVE ORGANS. 235 

and enter the blood by the gastric vein (Fig. 12-1 ; see also 
Fig. 127) ; the digested proteids, starch (sugar) for the 
greater part, leave the intestine by the mesenteric veins; 
these veins and the gastric vein pour their contents into the 
portal vein; the portal vein carries the food to the liver; 
the portal vein breaks up into capillaries through which the 
materials pass, and are collected into the hepatic veins which 
carry them to the ascending vena cava, by which they pass 
to the right auricle of the heart. 

The greater part of the digested fats with probably some 
of the digested proteids and starch are absorbed by the lac- 
teals of the intestine ; from these the absorbed materials 
pass through the mesenteric glands, and from these to the 
receptacle of the chyle (receptaculum chyli), the beginning 
of the thoracic duct; by the thoracic duct are carried along 
the posterior part of the thoracic cavity, and after making a 
small arch, empties into the left subclavian vein near its 
union with the internal jugular vein; .then into the left 
innominate vein from which it passes into the descending 
vena cava ; then into the right auricle of the heart 

Xotice that the materials absorbed by the lacteals have 
reached the same destination as those absorbed by the veins, 
but by a very different route. 

From the right auricle the material passes to the right 
ventricle, by the pulmonary artery to the lungs and after 
passing through the terminal capillaries is collected into 
the pulmonary veins and brought to the left auricle from 
which it passes to the left ventricle, and then into the aorta 
by whose branches it reaches the tissues of the various organs 
of the body. Carefully study diagram, Fig. 127. 

THE ACTION OF ALCOHOL OX DIGESTION AND THE DIGESTIVE 

ORGANS. 

The action of alcohol on any organ may be traced to one 
or to all of the following sources: (1) Its action on the blood 
vessels, causing the enlargement or dilation of the vessels, 
thus increasing the blood supply to the organ; (2) stimulat- 
ing through the nerve a more vigorous action; (3) the direct 



236 THE ALIMENTARY SYSTEM. 

effect on the cells of the tissue interfering with its normal 
metabolism. 

When taken in moderate doses, it causes a slight redden- 
ing of the mucous membrane, the degree of redness varying 
with the size and frequency of the dose. 

If alcoholic drinks be taken habitually, they will destroy 
the tonic condition of the blood vessels and produce in them 
a chronic congestion, more or less pronounced, as the habits 
of the individual are moderate or immoderate; and in ex- 
treme cases, they may bring about an ulcerated condition. 

When alcoholic drinks are not used habitually, but only 
occasionally, if blood vessels become dilated and congested, 
it is only temporary. They will return to their normal con- 
dition on ceasing the use of the alcohol. 

The first effect of alcohol on the process of digestion 
is to precipitate the pepsin of the gastric juice. But by the 
stimulating effect of the alcohol there is brought about an 
increased action of secretion, and the final result of a mod- 
erate dose of wine, brandy, or similar drinks is to aid 
digestion. 

It might be asked, then, if this is true, would not the 
constant use of alcohol be a good thing ? — Emphatically no. 
Its habitual use brings about exhaustion of the glands by 
overwork, a chronic congestion of the blood vessels, which 
conditions result in some of the worst forms of dyspepsia. 
There is great danger that its everyday use will create a 
love for alcoholic drink, a thing greatly to be feared. The 
physician should be very careful how he prescribes its con- 
stant use. 

It is to be doubted whether it interferes with digestion 
by coagulating the proteids of our food as stated in some 
works on physiology. It is true that eighty or ninety per 
cent alcohol will harden the white of an egg, but it should 
be remembered that alcohol is not taken this strong ; seldom 
over sixty per cent, and this diluted by two or three times 
its volume, so that when mixed with the food in digestion, 
it is diluted to a low per cent. A twenty or thirty per cent 
alcohol hardens a tissue very slowly. Try the experiment. 

Even in artificial digestion of fluids, if the alcohol does 
not form over eight or ten per cent of the liquid, it will 
not precipitate the pepsin nor interfere with the digestion. 



CHAPTER VIII. 

FOOD. 
EXPERIMENTS AND DEMONSTRATIONS. 

1. Weigh a small potato, and put in a drying oven (air 
bath) and keep at a temperature of 100° or 150° C. until 
thoroughly dried. If you have no drying oven, dry in the 
cook stove. Weigh the potato again. Determine the loss 
of weight due to drying. To what is the loss of weight due ? 
Dry a potato on a glass under a bell-jar, in the sun or on 
the radiator. What is the source of the moisture that col- 
lects on the side of the bell-jar? A large glass fruit can 
may be used in place of the bell-jar. 

2. Determine by Experiment 1 the proportion of water 
in the following: a ripe apple, lean meat, fat meat, cabbage, 
carrots, dried beef, and a fresh biscuit. Make a table of 
the per cent of water in the foods tested. 

3. Take the potato dried in experiment, and burn it in 
a porcelain crucible or in an iron sand bath. Weigh the 
ashes. What proportion of the potato is ashes? The ashes 
represent the amount of mineral matter in the potato. Test 
the ashes for the following: potassium, sodium, calcium, 
phosphates, and carbonates. (For tests see Appendix.) 

4. Determine the ash (mineral matter) in the following: 
lean meat, corn, wheat, beans, and egg. Test the ashes of 
each as in Experiment 3. Which seems to have the most 
phosphates ? the most potassium ? 

5. Thoroughly mince one or two ounces of suet or fat 
meat, and soak in three or four fluid ounces of benzine for 
forty-eight hours. Pour off the liquid, and set the liquid 
aside to let the benzine evaporate. (Keep the benzine away 
from the flame. ) What is the nature of the liquid you have 
left ? Weigh the liquid. How does the last weight compare 
with the first weight ? 

6. What per cent of butter is fat or oil? Test by dis- 
solving one-half ounce of butter in four or five times its 
volume of benzine. Does it all dissolve? Pour off the 

237 



238 FOOD. 

liquid into an evaporation dish or saucer, and set aside 
to let the benzine evaporate. Save the part that did not dis- 
solve, as you will need it in Experiment 14. What per cent 
of the butter is fat? 

7. Determine if the following contain oil: corn, wheat, 
oatmeal, Brazil nuts, walnuts, lard. 

8. Make some starch paste. Add to a small portion in 
an evaporation dish a few drops of a solution of potassium 
iodide (see Appendix), and then add a few drops of chlor- 
ine water ; the solution will turn purple or nearly black. 

9. Test the following for starch: corn, wheat, rice, oat- 
meal, tapioca, and beans. Grind each to a fine powder; 
make a paste, and test as in Experiment 8. 

10. Remove the peeling, and test some of the scrapings 
from the flesh of the following, for starch: potato, turnip, 
apple, and carrot. 

11. Place a drop of the liquid obtained from scrapings 
of the potato on a clean glass slip, put on cover glass, and 
examine with two-thirds and one-sixth objective. Make 
drawing. Examine in same drop of the liquids from the 
other objects taken in Experiment 10. 

Put a small amount of cornstarch on a slide, and add 
a drop of water. Examine with two-thirds and one-sixth 
objectives. Compare the size and form of the starch grains 
obtained in each case. 

12. Examine under high power a very thin slice of 
potato. Avoid two great pressure on the piece. Where are 
starch grains found ? 

13. a. To the white of an egg in a six-inch test tube 
add three or four times its volume of water. Stir thor- 
oughly, and place about one c.c. in a four-inch test tube, 
and boil. The heat causes the hardening (coagulation) of 
the albumin. 

b. To a fresh portion in a clean test tube add, drop by 
drop, ninety-five-per-cent alcohol until the albumin is coagu- 
lated. Try another portion with ten-per-cent alcohol. What 
difference do you note in the result? 

c. Heat another portion with nitric acid in a six-inch 
test tube, and note change of color to yellow. When cooled, 
add a few drops of ammonia water (ammonium hydroxide) 
which deepens the color (xantJio-proteic reaction). 

d. To another portion add a small amount of a solution 




PLATE IX. 

Figs. 72 and 73.— A Diagram of the Course of the Nerve Fibers in the Sub- 
stance of the Brain and Spinal Cord. 
(Study in connection with Plate X.) (After Aeby.) (From Eanney.) 

I. View of a transverse section. II. Profile view. III. The nuclei of the me- 
dulla (partly after Erb). The crosses of color correspondingto the lines upon which 
they are placed, designate the point of section of each tract as it passes through 
different levels (the crus and pons.) Ci. Internal capsule, with radiating fibers 
(in yellow), pyramidal fibers (red), and fibers going to the pons (in purple). PC. 
The crura cerebri, with the pyramidal fibers and the fibers going to the ganglia of 
the pons anteriorly, and posteriorly, the substantia nigra, the fillet tract (in 
dotted lines), the fibers of the superior peduncle of the cerebellum (in blue). 
Pc. The peduncles of the cerebellum, showing the fibers going to the cerebrum, 
the pons, and the medulla. P. Pons Varolii, with its ganglia on either side (in 
purple). 




PLATE X. 
Fig. 73. (From Ranney.) 

In III. the nuclei of the cranial nerve roots are numbered to correspond 
with the nerves. Red is used for the motor nuclei, and blue for the sensory 
nuclei. The tracts in the cord are designated by the area similarly colored in 
the cross-section of the cord beneath, c'. Column of Tiirck. c. Crossed pyram- 
idal column, a. Anterior horn. a'. Anterior root zone. e. Direct cerebellar 
rolumn. b. Posterior horn. b'. column of Burdach. d. Column of Goll. H'gher 
up are seen, b". The inferior peduncle of the cerebellum, d'. The fillet or 
lemniscus tract, f. the fibers connecting the ganglia of the pons with the cere- 
brum and cerebellum, b'". The fibers- of the superior cerebellar peduncle. 
h. The caudo-lenticular and thalmo-cortical fibers, i. The commissural fibers (see 
Fig. 6). Th. Optic thalamus, nc. Nucleus caudatus. nl. nucleus lenticularis. 
gc. Central convolutions. 

[In this diagram, the course of b"seems to be in error in not undergoing a 
decussation.— author.] 



EXPERIMENTS. 239 

of blue vitrol (copper sulphate) and an excess of caustic 
soda (sodium hydroxide) . The solution changes to a purple 
(Biuret or Piotrowsl'is reaction). 

e. Add to another portion a few drops of Millon's reagent 
(see Appendix) ; a white precipitate is produced. Boil, 
and note the change to pink. 

/. Test another portion with a solution of ammonium 
sulphate solution, which will precipitate the albumin when 
saturated with the solution. 

g. To one hundred c.c. of the solution of albumin add an 
excess of acetic acid and a saturated solution of Glauber's 
salts (sodium sulphate), which will give, on boiling, a white 
precipitate. 

The seven tests given above are the ones usually used for 
a class of substances called proteids. 

14. Test the following for proteids : lean meat, the pulp 
of fruits, cheese, beans, Graham flour, milk, butter, and bread. 
In case of milk, precipitate the casein with acetic acid, and 
filter. Dissolve some of the casein in lime water. See 
how many of the tests given in Experiment 13 apply to 
casein. Boil some milk, and apply test a. What reason can 
you give for the coagulation of milk on souring ? 

For the meat, put a small portion in cold water in a flask, 
keeping it at about 30° C. for an hour, and then boil until 
the meat is cooked. Test the solution obtained for proteids. 
Is there much of the meat that does not dissolve ? Test 
both cold and boiled solution of each of the other objects. 
What difference do you note ? 

15. Dissolve one or two small pieces of white stick candy 
in a test tube. To a small portion of the solution in a four- 
inch test tube, add fifteen or twenty drops of Fehling's solu- 
tion (see Appendix), and boil. A red precipitate (cuprous ox- 
ide ) is f ormed, due to the reducing power of the grape sugar. 

16. Test with Fehling's solution a solution of the fol- 
lowing: crushed grapes, syrup, honey, solution from germi- 
nating grains (wheat or rye), dates, maple sugar. In which 
do you find grape sugar (dextrose) ? 

17. To ten c.c. of a strong solution of cane sugar, com- 
mon granulated sugar (saccharose), add to the fifteen c.c. of 
Fehling's solution, and boil. Does cane sugar reduce the 
Fehling's solution ? How can you tell cane sugar from 
grape sugar ? 



240 FOOD. 

18. To twenty c.c. of a strong solution of cane sugar 
add two c.c. of strong muriatic acid (hydrochloric acid), and 
boil for an hour or more ; let cool. 

Test five c.c. of the solution with ten c.c. of Fehling's 
solution. Is the copper reduced? The acid changes the 
cane sugar to glucose. Repeat the experiment, using dilute 
sulphuric acid in place of the hydrochloric. 

19. Test a solution of milk sugar the same as in Experi- 
ment 17. 

20. Treat a half gram of starch with twenty or thirty 
c.c. of hydrochloric acid, and boil. After cooling, add fif- 
teen or twenty c.c. of Fehling's solution. Into what has part 
of the starch been changed? Repeat the experiment, using 
sulphuric acid in place of hydrochloric. Do you get the 
same result? 

21. a. Make a thick syrup of granulated sugar. To five 
or six c.c. of the syrup in a six-inch test tube add drop by 
drop strong sulphuric acid until the syrup turns black and 
becomes jelly-like. The black substance is the carbon of the 
sugar, the other parts of the sugar (hydrogen and oxygen) 
having been removed by the acid. 

b. Heat on a sand bath in an evaporation dish one or 
two grams of sugar until it is reduced to a black mass. 
What is this black substance ? 

c. Heat a gram of granulated sugar in a six-inch test 
tube; carefully watch for any moisture that may collect on 
the cooler parts of the tube. Heat until the sugar is reduced 
to a black mass. What is the source of the moisture that 
collects on the sides of the tube ? 

d. Show that meat contains carbon. 

FOOD. TEXT. 

Need of Food. — From a physical standpoint, our bodies 
may be considered as a machine, whose purpose it is to pro- 
duce motion, generate heat, and maintain life. 

It is the most wonderful of machines; it not only has 
the power of maintaining its activities, but also the power 
of growing stronger and larger by its own activities. 

Would it not be a wonderful engine that could, from the 
material put in its furnace, make its own wheels, rods, boil- 
ers, furnace, and other parts, and after years of use should 



NEED OF FOOD. 241 

be larger, stronger, and more efficient in its work ? Such a 
machine is the human body, and in the adaptation and per- 
fection of its parts, the possibilities of its movements, the 
most wonderful of machines. 

Xo machine can originate energy or do work of itself. 
The unwinding of the spring moves the works of the watch, 
but the spring is first wound so it will be on a tension. The 
engine of itself cannot pull the loaded train ; it can only do 
so when water is placed in its boiler and fuel in its furnace, 
so that heat set free by the burning of the coal causes the 
expansion of the steam, and the steam transfers its energy 
to the piston rods, and these in turn to the wheels. The 
energy here comes from the stored-up (potential) energy of 
the coal, set free in the form of heat (kinetic energy) by 
the burning of the coal. 

What fuel and water are to the engine, bread, meat, and 
many other foods are to the body. The bread and meat con- 
tain stored-up energy (potential), which may be set free by 
the cells of the body in the form of heat, nerve force, and 
muscular force. 

Our food must be more than an energy producer ; it must, 
in addition, furnish materials to repair the waste, and as the 
body is a self -constructing machine (in that it must grow), it 
must also furnish material for increasing the size of the 
organs. 

There are some of our foods which do not furnish energy 
to the body nor build up its active tissues. To this class belong 
those ( 1 ) which give consistency to tissue, as the water in the 
blood and the chondrin in cartilage; (2) that furnish a me- 
dium of exchange between the tissues, as the water in the 
blood and lymph ; ( 3 ) that furnish the proper condition for 
the chemical changes, as the alkalinity of the bile and pan- 
creatic juice, and the presence of soluble lime salts in the 
blood in relation to the coagulation of the blood. 

Foods * may be defined as those substances which may be 

i A clear distinction should be made between a food, a medicine, and a poison. 
A food, as we have seen above, Is a substance which is of use to the body in 
16 



242 



FOOD. 



appropriated by the tissues of the body, and be of use to it 

in the production of energy, building up tissue, or in aiding 

in or effecting any of its physical and chemical processes. 

Mineral Foods. — Of the mineral foods, water is the most 

abundant in the tissues of the body, making up sixty-five per 

cent of its weight in the adult, and over seventy per cent in 

the infant. The following table gives the amount of water 

in most of the organs of the body : — 

PERCENTAGE OF WATER AND ASH IN THE BODY. 

ASH. 



Skeleton 

Muscles 


22.0 

1.5 

1.3 

1.2 


Heart 

Pancreas 


... 1.1 
... 1.0 


Liver 

Spleen 


Brain and spinal cord 

Blood 

Kidneys 

Skin 


... 1.0 

9 


Lungs 

Intestines 


1.1 

1.1 


... 0.8 
... 0.7 



WATER. 



Adipose tissue 15.0 

Bones 50.0 

Liver 70.0 

Skin 70.0 

Spleen 77.0 

Muscles 77.0 

Brain and spinal cord 78.0 

Intestines 78.0 



Pancreas 78.0 

Blood 79.0 

Lungs 79 . 

Heart 79.0 

Kidney 83.0 

Lymph (Kirk) 90.0 

Vitreous humor 98. 7 1 

Cerebrospinal fluid 99. 0' 



Schenck and Giirber: Henry Holt & Co. 
Water is found in the flesh of animals, in eggs, fleshy 
fruits, and in various liquid foods, as coffee, tea, cocoa, etc. 
As our foods do not generally contain enough water for the 
needs of the body, it has to be taken alone. Water serves 
the following uses: (1) To give consistency to tissue, as in 
the blood and muscles; (2) as a solvent, and as such making 
possible chemical and physical processes, as osmosis, filtration, 
circulation, and chemical action of dissolved substances ; ( 3 ) 
as a regulator of heat by its evaporation from the surface 
of the body and the lungs ; (4) takes part in chemical changes. 
Other Minerals. — When the body is burned, these make 

keeping up its normal process; a medicine is a substance which tends to restore 
the normal processes when they have become deranged by disease; a poison is a 
substance which deranges the normal condition of the body. 

Which of these actions the substance performs depends upon the amount 
taken and the conditions under which it is taken. 



MINERAL FOODS. 243 

up the ashes. While they do not form a large part of the 
weight of the body, they serve a very important purpose. 

The Phosphates. — These are the most abundant of the 
salts of the body, being eighty per cent of their weight. They 
are derived from the tissues of animals and plants, and 
are especially abundant in grains of wheat, oats, and corn, 
and in animals in the muscles. Their importance in the 
body is: (1) As an important constituent of the cell, being 
essential to regeneration of the cell substance (potassium 
phosphate) ; (2) as a constituent of bone, and making up 
the greater part of the mineral of the bone (calcium and 
magnesium phosphate) ; (3) to aid in the coagulation of 
the blood. 

The Chlorides. — Next in abundance of the salts of the 
body is common salt (sodium chloride). It is found chiefly 
in the fluids of the body, and but little in the cells. It is 
not found in sufficient amount in our food, so that it is added 
to many of our foods, not only to heighten their flavor, but 
also to supply the demands of the body for this substance. 
Its more important uses are: (1) To aid in the solution of 
certain substances, as globulin; (2) to regulate the course and 
equilibrium of the flow of the liquid of the tissues 1 (osmotic 
pressure) ; i. e., it prevents the entering of water into the 
cells; (3) as material for the gastric gland, from which to 
make hydrochloric acid; (4) to stimulate muscular action. 

Potassium chloride is more abundant in the cell sub- 
stance than the sodium salt, but found but little in the fluids 
of the body. It is found in sufficient quantities in our food 
for the needs of the body. 

Carbonates. — The more important of these is calcium 
carbonate. The carbonates serve the following uses: (1) As 

i From what has been said, it will be seen why we add normal salt solution to 
fresh tissue when teasing them, rather than water. When tissues are placed in 
water, the cells become swollen, and the true structure of the tissue destroyed. 
If the tissue be placed in a solution containing more salt, then the tissue becomes 
shrunken by giving up its water to dilute the salt of the liquid in which it is 
placed, resulting also in the breaking down of the tissue. 

The normal salt solution is of the same degree of saltness as the liquid of the 
tissue, hence there is neither an inflow nor an outflow, and the proper consis- 
tency of the tissue is secured. 



244 FOOD. 

a part of the mineral of bone and the chief mineral of the 
grannies (otoliths) of the inner ear (calcium carbonate) ; 
(2) to aid in the excretion of carbon dioxide (calcium bicar- 
bonate and sodium bicarbonate) ; (3) to aid in the alkalinity 
of the tissne fluids (sodium carbonate). 

Salts of Iron. — These are important in the formation of 
the pigments of the blood. With the exception of common 
salt, all the above-named salts are contained in sufficient 
quantities in our food. 

ORGANIC FOOD. 

The organic foods may be divided into three classes: 
Carbohydrates, fats, and proteids. 

Carbohydrates. 1 — These include the sugars, starches, 
gums, and cellulose of our food, and are generally divided 
into, (1) the simple sugars (monosaccharides), including 
grape sugar and fruit sugar. They are found in fruits, in 
beets, onions, and in honey; (2) the double sugars (disac- 
charides), which include cane sugar, milk sugar, and maltose. 
All of these are important foods. Cane sugar is found in 
sugar cane, sorghum, sugar maple, beets, coffee, in many 
nuts, as walnuts, hazel nuts, almonds, and in honey. Sugar 
of milk (lactose) is found in the milk of various animals. 
Maltose is found in germinating grains, and in many malted 
liquors, in which it is formed by the action of the malt on 
the starch of the grains; (3) the complex sugars ('polysac- 
charides), which include starch, glycogen, dextrin, gums, 
and cellulose. 

Starch is found in most grains, in potatoes, and in green 
fruits. Starch is insoluble in water or the fluids of the body, 

i These were so named from their containing hydrogen and oxygen in the 
same proportion as found in water. We now know carbohydrates which do not 
have the hydrogen and oxygen in the proportion found in water. There are 
some compounds which have the hydrogen and the oxygen in the proportion 
found in water, which are not carbohydrates. The term, while it cannot be 
used in its original sense, has become so well fixed that it is not best to change 
it. When we first began to study these compounds, they were considered as 
simple ones, but we now know them to be very complex. The physiological im- 
portance of carbohydrates to the body is in the formation of glycogen and 
fat. The carbohydrates furnish material for combustion, which furnishes the 
body with energy for heat and for work. 



NATURE OF PROTEIDS. 245 

and would have no food value, but as it can be converted into 
sugar by the ferment (ptyalin) of the saliva and by the fer- 
ment (amylopsin) of the pancreatic juice, it is a very im- 
portant food. 

Glycogen, sometimes called animal starch, is found in the 
liver and in the muscles. It is not so valuable for its food 
qualities as it is important as the form in which the carbo- 
hydrates are stored up in an insoluble form and held in 
reserve until needed by the tissues. Glycogen is to the ani- 
mal body what starch is to the plant. 

Cellulose, found in various parts of the higher plants, 
is of little food value, as it is almost indigestible, but it is of 
interest in its relation to starch, as it makes the covering of the 
grains, and must be broken before the starch can be digested. 
It is, however, of great value to many animals, as sheep and 
cattle, as it is one of the chief constituents of the grasses. 

Fats and Oils. — These are found in the seeds and fruits 
of some plants, in milk, and in the tissues of animals. As 
they occur in our food, they are a mixture of two or more 
fats in varying proportions. 

The three more important fats are stearin, the chief con- 
stituent of tallow; palmitin, the principal part of human 
fat; and olein, the chief ingredient of most oils. Butter is 
a mixture of a number of fats. 

The oxidization of fats is one of the chief sources of heat 
to the body. They serve also other important uses, which 
have been mentioned. 

Proteids. — These are very complex 1 substances, com- 
posed of carbon, 50 to 55 per cent; hydrogen, 6.5 to 7.3 per 
cent; nitrogen, 15 to 17 per cent; oxygen, 19 to 24 per cent; 

and sulphur, 0.3 to 2.4 per cent. 

• 

i We know very little of the constitution, molecular weight, and formulae of 
proteid compounds. We know, however, that their molecular weight is very 
large and their structure very complex. 

" The crystallized serum albumin of the horse is supposed to have a molecu- 
lar weight of 17,070, and the empirical formula of C 7BB H, 21B N l96 S 10 236 ."— 
Schenck and Giirher. Compare the molecular weight and the formula just given 
with that of common salt, which has a molecular weight of 58.5 and the formula 
NaCl. 



246 FOOD. 

There is also present a small amount of phosphorus, iron, 
magnesium, calcium, potassium, and sodium. While these 
compounds in many cases bear a close relation to the proteid 
molecule, yet they are by most physiological chemists not con- 
sidered as essential to its structure. While they form no part 
of the proteid molecule, they are very important in relation 
to the work of the protoplasm. 

For the classes of proteids, see the diagram of the classi- 
fication of foods. As we shall use the term " proteid," the 
term includes the albuminoids, which differ chemically, phys- 
ically, and physiologically from true proteids. 

The more important proteids are albumin, casein, myosin, 
gluten, and legumin. 

Flesh of Animals. — The more important are the flesh of 
the ox, which furnishes beef ; sheep (mutton and lamb) ; pig, 
giving us pork, bacon, and ham ; and of domestic fowls. Of 
these, beef is the richest in nutritious matters, firmer, and 
more satisfying and strengthening, although mutton is con- 
sidered the more digestible. While the flesh of young ani- 
mals is more tender, it is more indigestible. Pork is quite 
indigestible, and contains a smaller amount of proteids, but 
a larger proportion of fat. Fish and oysters are rich in pro- 
teids, but poor in salts and fats. 

Flesh contains : ( 1 ) Proteids — myosin, globulins, serum 
albumin, gelatin, and elastin (from the connective tissue) ; 
(2) extractive, which gives flavor, as creatin, also sarcolactic 
acid, taurin, xanthin, and others; (3) mineral salts, the chief 
of which are those of sodium potassium, calcium, and mag- 
nesium, as phosphates, carbonates, or chlorides; (4) water, 
from fifteen to seventy-two per cent; (5) fats, from three to 
thirty-one per cent, including the common fats, as well as 
some of the more complex ones (lecthin and cholesterin) , the 
latter, however, is not a fat, but an alcohol, but with the fat 
acids forms fats) ; (6) carbohydrates, as dextrin, grape sugar, 
and, in the flesh of young animals, glycogen. For the com- 
position of the more important meats, see page 321. 

Milk. — For young animals, milk contains all the elements 



FOOD. 247 

of a typical food. Its principal constituents are: (1) Pro- 
teid substances, as caseinogen and serum albumin; (2) fats, 
various fats, principally in the cream; (3) carbohydrate, 
milk sugar (lactose) ; (4) salts, the chief of which is cal- 
cium phosphate; (5) water, a large percentage. 

The oil in milk is incased in a covering, consisting of case- 
inogen and serum albumins. By the process of churning, 
the oil globules are deprived of their covering, and the col- 
lected fats make up the butter, the proteid coverings being left 
in the buttermilk, and hence this liquid is rich in proteids. 
Cheese is principally casein, formed by the coagulation of 
the caseinogen by the. rennet ferments. The proportion of 
fats it contains depends largely upon the method of its manu- 
facture. While rich in proteids, it is difficult of digestion. 

Eggs. — These, like milk, contain the elements of a typical 
diet. They contain proteids in the form of egg-albumin and 
globulins, the most important of which is vitellin, found in 
the yolk, and nuclein, found in connection with iron. They 
also contain, in addition to the three common fats, yellow 
fat, lecithin (a very complex fat), cholesterin (an alcohol), 
and organic salts, of which the potassium chloride and phos- 
phates are the more important. 

Vegetables. — The vegetables richest in proteids are the 
fruits of the plants of the pulse family, represented in our 
food by peas, beans, and lentils, which contain a proteid 
substance called legumin (sometimes called vegetable albu- 
min), of which they contain 25.3 per cent. 

The grains of wheat, oats, and barley contain proteids in 
the form of gluten, which is a very valuable food materia^ 
and one of the important elements of bread. 

The pulps of ripe fruits, onions, and potatoes contain 
proteids. 

Albuminoids. — These are derivatives of the proteids, and 
are represented in our foods by elastin, from elastic tissues ; 
collagen, from connective tissue and cartilage, which, on 
boiling in water, yield gelatin. The albuminoids have little 
food value, as they cannot replace " the used-up body pro- 



248 FOOD. 

teids as the other proteids do." As a rule, they are diffi- 
cult of digestion. 

While they do not go to make up the cell substance, they 
are of importance in that they go to make up material for the 
skeletal parts of the body, as connective tissue, tendons, liga- 
ments, cartilage, and bone. 

The dualities of a Good Food. — A good food should pos- 
sess the following qualities : — 

1. It should contain the principles (proximate prin- 
ciples) contained in the tissues of the body, and in as near 
the same proportion as possible. 

2. It should be digestible. Chemically, a substance may 
pontain the elements needed by the body, but if they cannot 
be digested, it cannot be taken up by the blood, and by it 
distributed to the tissues. 

3. It must be palatable. An agreeable taste is one of 
the essentials to a good secretion of the saliva. Good insali- 
vation is an important part in securing good digestion. 

4. It must not be too concentrated. A certain amount of 
water and debris is essential to a good food. A diet consist- 
ing entirely of extract of meat, starch, and oils would be in 
the highest degree unwholesome. This is why fruits and 
vegetables should be added to our meat and bread. They 
give to the food bulk, and while they contain material that 
is indigestible, these indigestible materials serve a very im- 
portant part in exciting the peristaltic movements of the ali- 
mentary tract. Persons suffering from constipation should 
avoid concentrated food, eat Graham bread, fruits, vegetables, 
and drink freely of water. 

5. It should not be too dilute. The dilute food begets an 
undue enlargement of the stomach and intestines, as large 
quantities are required to give the body the proper amount 
of nutrient material. This excess of liquid tends to over- 
work the absorbent and excretory organs and produce corpu- 
lency. Hence beer as an article of diet is objectionable, and 
the truth of what has been said is well illustrated by those 
who use it freely, either as a drink or food, 



REASONS FOR COOKING FOOD. 249 

It should be remembered that there is a great difference 
in individuality, and the degree and concentration of our 
food must vary within certain limits, one person requiring a 
somewhat concentrated food, another requiring a more or less 
diluted food. We should, therefore, carefully watch the 
effect upon us of our diet, and choose the one that serves us 
best. 

Reasons for Cooking Food. — Much of our food is unfit 
for digestion in a raw condition. The more important rea- 
sons for cooking food are : — 

1. To soften and disintegrate the substances, as meats 
and many vegetables. 

2. To develop the flavor and render the food more pal- 
atable, as the baking of bread and meats. 

3. To protect the system from injurious germs that may 
infest our food, as bacteria in fruits, milk, and water, and 
parasites in dried fruits, meats, and cheese. Pork should 
never be eaten raw, as there is danger from trichina,, but 
should be cooked with especial thoroughness. 

4. To bring the food more nearly to the temperature of 
the digestive organs. When lower than that of the digestive 
organs, it retards digestion by lowering the temperature, and 
tends to congest or chill the mucous membrane. The thirst 
experienced by drinking ice water is produced by the irri- 
tating effect caused by the congestion it produces. Iced tea 
and similar beverages should be used with great care. 

Condiments. — Spices and other condiments should be 
used with care. The danger is not in their proper use, but 
in their abuse. Properly used, they are of importance (1) 
in rendering the food more palatable; (2) in acting as anti- 
septics, preserving the food; and (3) as stimulants to the 
muscular coats of the stomach and intestines (as carmina- 
tives), and also to increase the flow of the gastric juice (prob- 
ably more by reflex influence, by their action in the mouth, 
than by their direct effect on the stomach). A free use of 
them produces indigestion by overstimulation, and creates a 
morbid appetite. 



250 FOOD, 



CLASSIFICATION OP FOOD 

A. Mineral — Not Producing Energy 

I. Water. 

II. Salts. 

1. Carbonates. 

a. Calcium. 

b. Potassium. 

c. Sodium. 

d. Magnesium. 

2. Phosphates. 

a. Calcium. 

b. Magnesium. 

c. Potassium. 

3. Chloride. 

a. Sodium. 

b. Potassium. 

4. Salts of Iron. 

B. Organic — Energy Producing. 

I. Proteids. 

1. Simple Proteids. 

a. Albumins. 

(1) Serum Albumin. 

(2) Egg Albumin. 

(3) Lacto-albumin. 
(-J) Muscle Albumin. 

b. Globulins. 

(1) Serum Globulin. 

(2) Egg Globulin. 

(3) Fibrinogen (coagulated, becomes fibrin). 

(4) Myosinogen (coagulated, becomes myosin). 

2. Combined Proteids. 

a. Hemoglobin — found in the Blood. 

b. Mucins in the Mucous Membrane. 

c. Caseinogen (coagulated by acid, becomes casein). 

3. Albuminoids. 

a. Keratin (in membrane of nerves, in horny epidermal 

cells, hair, and nails). 

b. Elastin (from elastic fibers). 

c. Collagen (connective tissue, cartilage, and bone) — 

On boiling forms gelatin. 

II. Carbohydrates. 

1. Simple Sugars (monosaccharides). 

a. Grape Sugar {glucose or dextrose). 

b. Fruit Sugar {fructose or levulose). 

2. Double Sugars {disaccharides). 

a. Cane Sugar {saccharose). 

b. Milk Sugar {lactose). 

c. Malt Sugar {maltose). 

3. Complex Sugars {polysaccharides). 

a. Starch. c. Dextrin. 

b. Glycogen. d. Cellulose. 

III. Fats and Oils {Ethereal Salts). 

1. Palmitin ) 

2. Olein >• {Esters of Glycerin). 

3. Stearin ) 

4. Leci thins {Esters-like Compounds of Olycero-phosphoric Acid). 

5. Lanolin(Z£ster of Cholesterin). The cholesterins are alcohols. 



LIQUID POODS. 251 

Alcohol As a Food. — The question of the food value of 
alcohol is by no means settled. The results of equally skilled 
experimenters are conflicting, the difficulties to be over- 
come in solving the problem have not been surmounted, and 
much is yet to be learned of the digestive action of alcohol. 
While there is doubt as to its food value, there is no doubt 
that it is not an economical food; and it has no place in 
our list of food, as we generally use that term. We shall 
probably be near the truth to list it as a poison, with doubtful 
food value. W nile there is probably no doubt that it can oe 
completely oxidized in the system when taken in moderate 
doses, it is so strong a nerve poison that it should be given 
with great care, even in fevers, in which it was formerly 
thought to be of so great value as a food and to aid digestion. 
Do not give alcohol or alcoholic drinks when the patient is 
weak without the advice of a physician, and in every case 
watch the patient, 1 as it may prove harmful. 

Liquid Foods. — Water may be taken alone, or mixed with 
other substances to flavor or add to its food value by their 
solution in water. The more important of these are coffee, 
tea, and chocolate (cocoa). These contain certain aromatic 
principles, and an alkaloid, — in tea, called theine; in coffee, 
caffeine; and in cocoa, theobromine (similar to caffeine). 
In tea, in addition to the theine, there is tannic acid, which 
acts on the blood vessels, causing their contraction {astrin- 
gent), and lessening the secretions. This action is intensified 
by the action of the theine, the result of which is a tendency 
to constipation. Persons suffering from this trouble should 
use tea very sparingly, and, in fact, would be better without 
it. Coffee, on the other hand, is free from tannic acid, and 
with many persons acts as a laxative. Cocoa also contains 
tannic acid, and, in addition to the substances found in coffee 
and tea, it contains fat, albuminous matter, and starch, and 
is, therefore, more of a food. 

i"If the pulse becomes quick and feeble, or, as indicating gastric irritation, 
the tongue becomes dry and brown, or the skin hot and dry, or the breathing 
hurried, or the patient suffers from insomnia, the alcohol should be stopped. 
On the other hand, if the pulse becomes stronger and slower, the tongue and 
skin moist, the breathing tranquil, and the patient sleeps well, the drug is doing 
good." — White and Wilcox. 



252 FOOD. 

Caffeine and theine are cerebral and heart stimulants., 
The person becomes wakeful, the mental activity and capabil- 
ity for work are increased, and the reasoning power is affected 
as much as the imagination. It is also believed that in man 
caffeine increases the power of muscular endurance, and 
this view seems to be supported by the results of the use of 
coffee in the army and navy. These drinks, however, should 
be used with moderation, as their immoderate use, more 
especially in the case of tea, will injure the heart and nerv- 
ous systems, and produce dyspepsia. 



CHAPTER IX. 
THE CIRCULATORY SYSTEM. 

EXPERIMENTS AND DEMONSTRATIONS. 

A. Materials. 

1. Sharp knife. 2. Probe. 3. Cotton or rags. 4. Fresh 
specimen of sheep's or ox's heart and kings, showing the peri- 
cardium unbroken, and also part of the diaphragm. 

B. Terms. 

1. Dorsal, side of heart turned toward vertebral column. 
2. Ventral, side next to sternum. 3. Right and left, proper 
right and left side of the heart when in natural position. 4. 
Anterior, toward the head in the natural position of the 
parts. 5. Posterior, the parts turned away from the head. 

C. Method. 

I. Hold up specimen by windpipe (trachea) so that you 
can best view the heart; notice the relation of the heart to, 
1. Lungs. 2. Diaphragm. 3. The manner in which the sac 
(pericardium) invests the heart. 

II. Place specimen on table with ventral side uppermost, 
and carefully dissect away fat, etc. 

Trace vessels, the one on the abdominal side of the dia- 
phragm to where it enters the pericardium. In order to do 
this, — 

1. Turn right lung toward your left. 2. Turn heart 
toward your right. 3. ^Notice entrance into pericardium 
about three inches from where it enters the diaphragm. 

a. This vessel is a vein (vena cava inferior). As soon as 
a vessel is found, clean it, and stuff it. 

b. The one which comes from above enters the peri- 
cardium about an inch above vena cava inferior. This vessel 
is also a vein (vena cava superior). 

c. The vessels between the vena3 cavse coming from the 
right lung enter the pericardium. Trace the vessels as far 
as you can from the heart to the right lung. These are the 
two right pulmonary veins. 

253 



254 THE CIRCULATORY SYSTEM. 

III. Turn right lung and heart back to natural position. 
Clean away loose fat from the front of pericardium, and 

seek and clean the following vessels in the mass of tissue 
lying anterior to the heart, on the ventral side of trachea. 

1. The one which, immediately on leaving the pericar- 
dium, gives off a large branch; then arches back and runs 
down behind the heart (the aorta). 

2. The one imbedded in fat on dorsal side of aorta (pul- 
monary artery). Trace its course. Notice nature of the 
walls of the last-mentioned vessels. 

IV. Slit open the pericardium. Notice the surface thus 
exposed. Then cut away the pericardium from the entrance 
of the various vessels already traced. 

The one on the ventral side of the pulmonary artery 
(left pulmonary vein). Trace this vessel. 

V. Notice position of pulmonary artery and aorta. Very 
carefully dissect out the pulmonary veins in the heart. Note 
the following : — 

1. Upper flabby portion into which the veins open (auric- 
ular portion). 

2. The denser lower part (ventricular portion). 

3. Look for band of fat running around the top of the 
ventricles, a branch of which runs obliquely down to the front 
of the heart, passing to the right of its apex, and indicating 
externally the position of the internal partition of septum 
which separates the right ventricle, which does not reach the 
apex of the heart, from the left, which does. 

4. Note the fleshy appendages, one below the pulmonary 
artery (left auricular appendage), the other between the 
aorta and superior vena cava (right auricular appendage). 

VI. Dissect away very carefully the fat around the great 
arterial trunks and base ventricles. Look for — 

1. A branch arising from the aorta close to the heart, 
opposite the right border of the pulmonary (right coronary 
artery). Trace its branches. 

The groove which one of its branches follows marks the 
line between the right auricle and the ventricle. 

2. The other much larger arising from the aorta dorsal to 
the pulmonary artery (left coronary artery). Its main 
branch marks the ventral edge of the ventricular septum. 



EXPERIMENTS AND DEMONSTRATIONS. 255 

3. The veins which accompany the coronary arteries 
(coronary veins). 

VII. Open right ventricle by placing knife through the 
heart about an inch from the upper border of the ventricle, 
and on the right of the band of fat marking the limits of the 
ventricles (see previous article), and cut down to the apex, 
keeping to the right of the line; cut off the pulmonary artery 
about an inch from its origin from the heart. 

1. Open the right auricle by cutting a bit out of its walls 
to the left of the entrance of the vena cava. 

2. On raising up by its point the wedge-shaped flap cut 
from the wall of the ventricles, look for cavity of the ventricle, 
which examine with care. 

a. Pass handle of probe from ventricle into pulmonary 
artery. Mark thoroughly the relation, b. Slit open the 
auricular appendages, and notice — 

(1) Fleshy projections (columnce carnce). 

(2) Mature of the rest of the surface. Xote numerous 
small openings (foramina Thebesii). 

(3) Apertures of the vena cava. 

(4) Below the entrance of the inferior vena cava notice 
opening of coronary sinuses; pass probe through and along 
the sinus, and slit it open ; notice muscular layer covering it. 
Raise the flap by its apex, and cut out the ventricular wall, 
and if necessary prolong the cut more toward the base, until 
divisions of the auriculo-ventricular valves (the tricuspids) 
come in view. Examine closely, and notice — 

(a) Muscular cord stretched across its cavity (not found 
in human heart). 

(b) Prolongation of the ventricular cavity toward the 
aperture of the pulmonary artery. 

(5) Cut away the right auricle and examine carefully 
the tricuspid valves. Xotice — 

(a) Tendinous cords (chordae tendinece). 

(b) Attachment to ventricle walls (musculi papillares), 
which are attached by one extremity to the walls of ventricles, 
the opposite extremity giving attachment to chordae tendinese. 

(c) Examine valves of pulmonary artery (semilunar 
valves). 

(d) Xotice in the middle of the free edge of the semi- 
lunar valves a little nodule (corpus aurantii). 



256 THE CIRCULATORY SYSTEM. 

VIII. Open left ventricle in a manner similar to that 
employed for the right. 

1. Open left auricle by cutting a bit ont of its walls above 
the appendage. 

2. Cut the aorta off, about half an inch from its origin 
from the heart. 

3. Examine, 

a. Aperture between left auricle and ventricle (left ven- 
tricular opening). 

b. Passage from ventricle to aorta. 

c. Entry of pulmonary veins to left auricle. 

d. Partition (septum) between. 

e. Auricles. 
/. Ventricles. 

4. Pass handle of probe, 

a. From ventricle into auricle. 

b. Another from ventricle into aorta. 

c. Probe into points of entrance of pulmonary veins. 
Notice that no other veins enter this auricle. 

d. Slit open the auricular appendage; notice fleshy pro- 
jection (musculi pectinati). 

(1) On interior of auricle. 

(2) Those over the inner surface of the ventricular wall. 

(3) Smoothness of the rest of the surface of auricle. 

(4) Thickness of ventricular wall as compared with 
right ventricle or auricles. 

5. Carefully raise wedge-shaped flap of the left ven- 
tricle, and cut on toward the base of the heart until the 
valve (mitral) between auricle and ventricle is brought to 
view. 

a. Notice, 

(1) Position of the flaps. (2) Texture. (3) Chorda? 
tendinese. (4) Columnse carnea?, etc., as in case of right 
side. (5) Semilunar valves of aorta. 

b. Cutting up carefully between two of them, examine 
the bit of aorta still left attached to heart. 

c. Note the origin of the coronary arteries in two of the 
three dilations (sinuses of Valsalva) of the aorta wall above 
the semilunar flaps. 

IX. Examine piece of aorta, and notice, 

1. Thickness of its walls. 2. Extensibility in all direc- 



EXPERIMENTS AND DEMONSTRATIONS. 257 

tions. 3. Its elasticity. 4. That it does not collapse when 
empty. 

X. Examine piece of a vein, and compare structure with 
that of the artery. How do the pulmonary artery and aorta 
compare with the venae cavse and the pulmonary veins in 
their structure and properties ? How can you account for 
this difference ? Does a transverse section under the micro- 
scope show any difference in structure? Why should the 
arteries differ in their structure from the veins ? 

Heart Muscle Cell. — Take a small piece of a fresh speci- 
men of the heart. Tease in normal salt solution (six-tenths 
per cent salt) until in very fine threads. Examine with 
microscope, first with two-thirds objective and then with 
one-sixth objective. Make careful drawing of what you ob- 
serve. Xotice, 

1. That it has no sarcolemma. 

2. That the cells anastomose (define the last term) . 
Queries. — 1. Where is the coronary valve, and what is its 

function ? 

2. What is the difference in structure of the heart of an 
earthworm, a snail, a fish, a snake, a bird, and a mammal ? 

3. What animals contain a nodule of bone in the heart? 
Where? Why? 

4. What animals have blood but no heart ? 

5. How many hearts has the earthworm ? 

G. Compare structure of a cell of heart muscle, of vol- 
untary and of involuntary muscular fiber. 

TO SHOW THE GEXEEAE PRIXCTPLE OF CTRCUEATIOT*. 

1. Apparatus. — A bulb syringe ; two yards of elastic rub- 
ber tubing ; two yards of inelastic rubber tubing ; short pieces 
of glass tubing of different sizes, some drawn out into short 
jets, others into long ones of almost capillary bore, and a 
basin of water. 

2. Manipulation. — Attach to one end of the syringe the 
inelastic tubing; now place the other end of the syringe in 
the water. Press upon the bulb, release the pressure, repeat 
the process until the tube is full of water. Press forcibly 
upon the bulb, and see how far you can send the water. Is 

17 



258 THE CIRCULATORY SYSTEM. 

the stream constant ? In the experiment, to what would 
the bulb correspond ? The pressure upon the bulb ? The 
release upon the bulb ? The alternate spurting ? Place the 
finger lightly upon the tube when water is being forced 
through it by the bulb. Do you feel anything that corre- 
sponds to the pulse in the arteries ? 

Now try similar experiments by putting in the opposite 
end of the tube one of the jet tubes. Repeat the experi- 
ment with various tubes. Note carefully any change that 
may be made in the force or constancy of the stream due 
to the size or length of jet. 

Repeat the experiments, but use instead of the inelastic 
tube, the elastic tube. 

Note change in constancy of the stream when the jet 
tubes are used ; also the more marked pulse movement. From 
these experiments we may learn, 

a. That the contraction of the heart (systole of the ven- 
tricle) forces at intervals a quantity of blood with a certain 
force into the aorta. The bulb representing the heart; the 
tube, the aorta. 

b. By the blood vessels becoming smaller, there is offered 
to this force a resistance (peripheral resistance) as the arter- 
ies become smaller, lessened when their bore is increased by 
relaxation of their muscular coats. In the experiment of 
jets of different sizes, illustrate the cause of this resistance, 
also the effect of increase of size of vessels. 

c. The arteries being elastic, we have a long stretch of 
elastic tubing from the heart to the capillaries. As in the 
experiment, so in our bodies, these elastic tubes give con- 
stancy to the flow. 

d. Bv connecting with the main elastic tube a three- 
way tube, to which is attached elastic tubes ending in jet 
tubes, it will be learned that the greater amount of fluid will 
flow in the tube in which the peripheral resistance is the 
least ; i.e., through the tube having the largest opening. So 
it will be in the arteries. If in any part of the body the 
peripheral resistance is increased by the contraction of the 



EXPERIMENTS AND DEMONSTRATIONS. 259 

muscular coat of the artery, aud the resistance of another 
part of the body lessened by the relaxation of the muscular 
coat, the blood will now from the region of great resist- 
ance to that of small resistance. 

Queries. — 1. Why should fear cause an increase of the 
heart' s beat ? 

2. What physiological fact does blushing illustrate? 
Growing pale ? Give reason for the difference. 

3. Why is there more blood in the digestive organs dur- 
ing digestion? 

4. Are the blood vessels of the digestive organs in a state 
of relaxation or contraction? 

1. The Arteries. — If you have an injection apparatus, in- 
ject the aorta from the left ventricle. To do this, before kill- 
ing the cat or rabbit determine the position of the heart by the 
beat upon the thoracic wall. After killing, make an incision 
to the left of the sternum, and at such a level as will be most 
convenient to reach the left ventricle. The left ventricle may 
be told from the right by its firmer walls. Make an in- 
cision in the left ventricle large enough to admit the canula. 
Force the canula up into the aorta, and tie firmly in posi- 
tion by thread wrapped around the aorta. Now fasten to 
the canula the piece with the stop-cock. Before injection 
clean the part from blood by the use of a moist sponge. 
Fill the syringe with injection mass (see Injection Mass 
below), place in the piece with stop-cock, which should be 
open, and press gradually upon the piston until the syringe 
is emptied : before removing the pressure, close the stop-cock 
so as to keep the mass in the arteries. Repeat the process 
until the injection mass gives color to the very small arteries. 

2. The Veins. — Prepare another cat or rabbit ready for 
dissection. Remove the skin from the thigh, and on the 
inner side, between the two great muscles of this part, look 
for a large vein (femoral). Ligature the vein in two places 
about an inch apart. Make an incision large enough to 
admit a small canula. Insert canula so as to point toward 
the heart, and tie firmly in place, and cut the upper liga- 
ture. Inject in the same manner as you did the artery. 



260 THE CIRCULATORY SYSTEM. 

Carefully dissect out the vessels, using great care in the 
separation of tissues and muscles. 

3. The Capillaries. — Catch a tadpole, and dehydrate by 
putting in sixty per cent alcohol for two hours, then in 
seventy- five or eighty per cent. Then color by putting in 
hematoxylin for eight or ten hours. Again put in alcohol 
ninety to ninety-five per cent, then in turpentine, and mount 
in dammar. Use two-thirds objective and eyepiece. Exam- 
ine also with one-fifth objective. 

4. Injection Mass. — One of the best injection masses is 
made as follows : — 

1. Make a solution of dichromate of potash, about half 
a pint. 

% Add to the solution a solution of acetate of lead as 
long as a precipitate is formed. Let the precipitate settle. 

3. Pour Off the fluid from the precipitate, and wash the 
precipitate until it is free from acid. To do this, add water 
to the precipitate, stir thoroughly, let it settle, and pour off 
the fluid. Repeat as often as is necessary. 

4. To about three pints of water placed in a vessel over 
a water bath, add white glue, and heat until the mass 
has the consistency of a thin gravy. 

5. JSTow add enough of the precipitate to give the mass 
a bright yellow color. Set away to cool. Warm before 
using, and keep warm while using. 

5. Queries. — 1. Erom what has been given trace the cir- 
culation of the blood from the right auricle to the left ven- 
tricle ; from the left ventricle to the right auricle. How do 
these circulations differ (a) in the color of the blood which 
flows through the arteries and veins and (b) in their pur- 
pose ? 

2. What artery carries venous blood, and what vein 
arterial blood ? 

3. What large blood vessels would be cut by an amputa- 
tion of the lower limb just below the knee ? In the amputa- 
tion of the arm above the elbow? 

4. Trace the blood from the left auricle to the palm of 
the hand and back to the right auricle, naming the large 
vessels through which it would pass (see chart). 



EXPERIMENTS AND DEMONSTRATIONS. 261 

5. Why can you not inject the veins from the right 
auricle 1 How much of the venous system can be injected 
from the femoral vein ? Give reason for your answer. 

6. In what part of the body does the blood have to 
pass through a double system of capillaries before it returns 
to the heart ( 

7. What veins end in capillaries ? 

8. In case of a wound, how can you tell an artery from 
a vein ? What difference should be made in the application 
of pressure to prevent bleeding ? Why ? 

G. To Make a Permanent Mount of Blood — Take a clean 
slide ; near the center spread on very thinly a small amount 
of freshly drawn blood ; gently warm over an alcohol flame, 
until dry (avoid getting too hot). When the slide has cooled, 
make a ring of Bismarck black of the size of the cover; let 
ring dry; when dry, gently heat the slide from the side 
opposite the ring; now carefully put on the cover glass (do 
not heat too much, only enough to make the cover glass 
adhere to the ring). 

7. To Examine the Blood, Fresh. — Spread on the slide 
a small amount of blood, and then put on the cover glass. 
The thinner the layer of blood the better view you will 
have of the corpuscles. 

Ex*amine blood of different animals; make drawings of 
what you observe. 

1. When you kill a chicken, collect the blood; divide it 
into two portions ; set the first aw T ay, and notice at intervals 
of a few minutes any changes that may take place. Stir 
the second portion with a bunch of wires or twigs. In a 
short time the fibrin will collect on the wires, and if the 
process is continued all the fibrin may be removed. The 
fibrin thus obtained will be red from the corpuscles; these 
may be removed by washing in water, and when clean, the 
fibrin will be white and in the form 1 , of highly elastic 
threads. After the fibrin has been removed, the blood is 
called defibrinated blood. 

2. If platinum wire or foil can be obtained, dip one 
end in the freshly drawn blood, then hold it in the alcohol 
flame for a short time, when it will become coated with black, 
showing the presence of carbon in the blood. Continue to 
hold it in the flame, and finally notice that an ash will be 



262 THE CIRCULATORY SYSTEM. 

left on the wire, showing the presence of the mineral con- 
stituents. 

3. To a drop of blood, add a drop of acetic acid and 
examine with the microscope; to another drop on the slide, 
add some fresh water, and carefully note with the micro- 
scope the change in size, and to the third, add some alcohol, 
and examine as before. Give reasons for each of the above 
changes of shape and size of the corpuscles. Make drawings. 

4. Take from a sore some of the matter, and examine 
for colorless corpuscles. Make drawing for any change of 
form that may be observed. 

In any of the above experiments, where it is desired to 
have the corpuscles retain the vitalitv, it is best to keep them 
moistened with a normal salt solution (six-tenths per cent) 
and let the slide be kept warm, as directed in Appendix. 

8. The Circulation of the Blood. — Take a piece of a thin 
board, as a chalk-box lid, and cut in it near one end, a tri- 
angular hole an inch on a side." Obtain a frog, and hold- 
ing it firmly in the left hand, make with scalpel a small 
incision in the skin on top of the head; now insert beneath 
the skin a piece of urari 1 about one fourth the size of a 
pin head. Let the frog free in the room, and in a few 
minutes it will be ready for use. The poison paralyzes 2 
the voluntary muscles, but seems to have little effect at first 
upon the involuntary muscles, hence respiration and circu- 
lation will be normal or nearly so. Place the frog upon 
the thin board, and tie the web over the hole by means of 
threads attached to the toes. The threads may be held in 
place by slits cut inside of board or by small tacks driven 
in edges of the board. Place the board on stage of micro- 
scope so that the web may be illuminated by the mirror 
below the stage, and brought in focus with the objective 

i Urari (Indian arrow poison) is very poisonous, and should not be handled if 
the skin on the hand is in any way broken, as it may be absorbed by the blood 
and produce poisoning. To remove the urari from the scalpel, soak it in dilute 
alcohol. Always remove the urari from the scalpel after the experiment. 

2 More properly speaking, the poison paralyzes the end plates of the nerves 
rather than the muscle or the entire nerve, or the center from which it comes. 
In the involuntary muscles, nerve endings are paralyzed and death is produced 
by paralysis of respiration. If, however, the dose is not too large, th<i excretory 
organs will carry off the poison, and the animal will recover. The drug is also 
called curara, woorara. 



THE HEART. 263 

above. Use a three-fourths objective. Cover the frog over 
with a moist cloth, leaving only the web exposed. Remem- 
ber urari is very poisonous, and must be used ivith the 
greatest care. 

JSTotice carefully the rate and mode of the circulation. 
Do you notice any change in the form of the red corpuscles ? 
Why are they not red ? 

Good results may be secured without the use of urari, by 
simply tying the frog fUmly over the body by a band of cloth. 

Another very good method is to put salamanders into a 
clean glass jar, and place the jar in a strong light. Cause 
the salamanders to crawl up the sides of the jar and as 
the webs are spread out on sides of the jar before you, you 
can examine with reading glass or simple microscope lens 
(50 or 60 diameters). This is worth trying, as you will 
be able to view the circulation under normal conditions. 

CIRCULATION. TEXT. 

Position of the Heart. — The heart (Fig. 128) is situated 
in the thoracic cavity in the space between the lungs, and is 
placed obliquely. The base, or attached portion, is directed 
upward, backward, and to the right; the apex, forward, 
downward, and to the left. It is placed behind the lower two 
thirds of the sternum, and projects farther to the left than 
to the right, and one and a half inches to the right. It extends 
(Fig. 128) from the second to the space between the fifth 
and sixth ribs. 

The Pericardium. — The heart is invested by a fibro-serous 
membrane, the pericardium. The sac is conical in shape, 
with its apex above, where it surrounds the great blood ves- 
sels about two inches from their origin. Its base is attached 
to the central tendon and part of the adjoining muscular 
structure of the diaphragm. Behind it are the bronchi, the 
esophagus, and descending aorta. Laterally descending be- 
tween it and the pleura is the phrenic nerve. 

The pericardium consists of two layers. The outer 
{fibrous) is a strong, dense membrane. Above, it invests, 



564 



THE CIRCULATORY SYSTEM. 



by a tubular prolongation, the large blood vessels, which have 
their origin from the heart, and becomes gradually lost upon 
their external coats. The inner (serous) invests the heart, 
and is then reflected on the surface of the fibrous layer. 




Fig. 128. — Position of the Heart. 
1. The heart. 2. Third costal cartilage. 3. Fifth intercostal space. 4. Black 
line marks the outline of the lungs. 5. Sternum. 

Parts of the Heart, — The heart is a double organ (Figs. 
129 and 130), separated by a muscular septum into the right 
and left sides. Each half is divided by a constriction into an 
upper portion (auricle) and a lower portion (ventricle). 
This division is indicated by the transverse groove (auriculo- 
ventricular), ' 







PLATE XL 

Fig. 76.— A Diagrammatic Figure Showing the Cerebral Convolutions. 
(Modified from Dalton.) (From Eanney.) 

S. Fissure of Sylvius, with its two branches, a, and b, b, b. R. Fissure of 
Rolando. P. Parieto-occipital fissure. 1, 1, 1. The first, or superior frortal con- 
volution. 2, 2, 2, 2. The second, or middle frontal convolution. 3, 3, 3. The third 
frontal convolution, curving around the ascending limb of the fissure of Sylvius 
(center of speech movements). 4, 4, 4. Ascending frontal (anterior central) con- 
volution. 5, 5, 5, Ascending parietal (posterior central) convolution. 6, 6, 6. 
Supra-Sylvian convolution, which is continuous with 7, 7, 7, the first or superior 
temporal convolution. 8, 8, 8. The angular convolution (or gyrus), which becomes 
continuous with 9, 9, 9, the middle temporal convolution. 10. The third, or 
inferior temporal convolution. 11, 11, The superior parietal convolution. 12, 12, 12. 
The superior, middle, and inferior occipital convolutions, called also the first, 
second, and third (the centers of vision). It is to be remembered that the term 
"gyrus" is synonymous with "convolution," and that both terms are often 
interchanged. 



THE HEART. 265 

Openings of the Heart — The openings of the heart 
are: — 

1. To the Auricles. — a. The right: the vena cava su- 
perior, vena cava inferior, coronary sinus, and vena? thebesii. 
b. The left : the four pulmonary veins, entering the heart by 
two trunks. 

2. From the Ventricles. — a. From the right ventricle, 
the pulmonary artery, b. From the left ventricle, the aorta. 

3. Within the heart, between the auricles and ventricles, 
the auriculo-ventricular orifice. 

Valves of the Heart. — 1. Between auricles and ventricles 
(auriculo-ventricular) . a. On the right side, the tricuspid, 
formed by a duplicating of the lining membrane of the heart, 
strengthened by a layer of fibers containing, according to 
some authorities, muscular fibers. They consist of three seg- 
ments of triangular shape, which are connected by their bases 
and by their sides with one another, so as to form a continu- 
ous annular membrane. To their free margins and their 
lower surface are attached the delicate tendinous cords 
(chorda? tendinece) extending to some of the muscular pro- 
jections (musculi papillaries) from the wall of the ven- 
tricles, b. On left side, the bicuspid, or mitral. It is sim- 
ilar in attachment and structure to the tricuspid, but stronger 
and larger, and consists of two segments of unequal size. The 
tendinous cords are thicker and stronger, but fewer in num- 
ber. Xotice the various ways by which greater strength is 
given to the left ventricle. 

2. In blood vessels going from the ventricles — the semi- 
lunar valves, a. Pulmonary valves. These are two in num- 
ber (by some authorities three), formed by the duplication 
of the lining membrane of the heart, strengthened by fibrous 
tissue. They are attached by their bases so as to form pocket- 
like valves. In the center of the free edge of the valves is a 
small, fibrous nodule (corpus Arantii). b. Aortic valves. 
These are three in number, and they are similar in structure 
to the pulmonic, but are larger, stronger, thicker, and the 
markings on the surface (fibers from the corpus Arantii) 



266 



THE CIRCULATORY SYSTEM. 



are larger and more prominent than those of the right side of 
the heart. 1 

Structure of the Walls of the Heart — The walls of the 
heart are muscular, and made of fibers having a very complex 
arrangement. They may, however, be put into two classes: 
( 1 ) Those of the auricles, which are arranged in two layers, 
— a superficial layer common to both auricles ; a deep-seated 
layer, proper to each auricle, consisting of looped fibers pass- 
ing upward over each auricle. Annular fibers surround the 
whole of the auricular appendage and are continued on the 




Fig. 132. — Eel ati ve Area of the Aorta, Total Caliber 
oe Capillaries and Venjs Cav^e. 
1. Aorta. 2. Total caliber of capillaries. 3. Venae cavse. 

walls of the vessels which have their origin from the auricles. 
(2) Those of the ventricles. These are arranged in numer- 
ous layers. Their arrangement is very complex. The general 
direction of the external layers is nearly inclined from left to 
right as they run downward, while that of the internal is 
just the reverse, nearly vertical, running upward from left 
to right. 

These muscular walls are covered on their pericardial 
surface by the cellular layer, on the inner surface by the 
endocardium, which by its reduplication assists in forming 

iln addition to the valves mentioned there are the following:— 

1. The imperfect valve (Eustachian) at the mouth of the inferior vena cava, 
which in the adult serves no very important purpose, but in the first stages of 
the individual, serves an important function in directing the blood through tho 
foramen ovale. 

2. The valves of the coronary veins, which, to a degree, prevent the reflux of 
the blood into these veins during the contraction of the auricles, 



THE HEART. 267 

the valves, and is continuous with the linings of the great 
blood vessels. On the internal surface of the auricular 
appendages are muscular columns (musculi pectinati). 
From nearly the whole inner surface of the ventricles project 
rounded muscular columns (columnar carnece). The mus- 
cular walls of the left side are much thicker than those of the 
right side. 

Size and Weight of the Heart. -In the adult the heart 
is about five inches in length, and three and a half in breadth 
in the broadest part, and two and a half inches in thickness. 
The average weight, in the male, varies from ten to twelve 
ounces; in the female, from eight to ten ounces. The pro- 
portion to body weight is 1 to 169 in the male, and in the 
female, 1 to 149 (Gray). The heart continues to increase 
in weight and size up to an advanced age. This increase is 
more marked in men than in women. 

Nutrition of the Heart. — The heart is nourished by the 
coronary arteries, which arise from the aorta, just above the 
free margin of the semilunar valves, the right coronary 
artery going to the right border and the left going to the left 
border. It arises a little higher than the right, and is some- 
what larger. Why should it be larger ? These arteries break 
up into numerous branches over the surface and substance of 
the heart. The veins of the heart accompany the arteries. 
The veins are the great cardiac vein, the anterior, middle, 
and posterior cardiac veins, and numerous small veins (vena? 
cordis minima?), which enter the heart by independent open- 
ings (foramina Thebessi). 

Nerves of the Heart. — The nerves are derived from the 
cardiac plexus. The nerve cells, or ganglia, are distributed 
at the junction of the sinus with the auricle and also 
along the entering nerve (sinus ganglia) at the junction of 
the auricle and ventricle. There are also ganglia found on 
the auricle. In addition to these ganglia, the heart receives 
nerve fibers from the pneumo gastric nerve (par vagum), 
which gives to the heart augmentory and inhibitory fibers. 1 

i In the dog It has been found that the augmentory fibers leave the spinal 
cord by the anterior roots of the second and third dorsal nerves, and possibly, 



268 THE CIRCULATORY SYSTEM. 

Arteries. — The wall of the small artery (Fig. 133) which 
is soon to break up into capilliaries consists of, 

1. An inner lining of cells similar to that making up 
the wall of the capillary, resting upon a thin, transparent, 
structureless membrane (basement membrane). 

2. A layer made up of connective tissue in which are 
imbedded muscular fibers (middle or muscular coats). 




Fig. 133. — Section of an Artery oe a Cat. 

1. Endothelial layer. 2. Inner layer (intima). 3 Nucleus of muscular cells 
of middle coat. 4. Elastic fibers. 5. Middle coat (tunica media). 6. Outer coat 
(tunica adventitial (0. W. B.) 

3. A layer of connective tissue containing a relatively 
large number of elastic fibers (external coat). 

It will be seen that the effect of this increase of thick- 
ness is to render the walls of the artery less permeable, and 
the power of the interchange of materials through its walls 
is to a great degree lost. 

When the artery breaks up into capillaries, these coats 
disappear, the muscular coats sometimes continue for a short 
distance, and all that is left of the outer coat is a little con- 
nective tissue. 



to some extent, by the fourth and fifth, passing along the rami communicans 
into the stellate ganglia, and passing upward through the annulus of Gimssens 
to the inferior cervical ganglia, and thence along cardiac to the superior vena 
cava and heart. The inhibitory fibers which come by way of the spinal acces- 
sory, pass through the ganglion (trunci vagi), along the trunk of the vagus, 
and by branches to the superior vena cava and the heart. 



THIS CAPILLARIES. 



2G9 



The larger arteries 1 resemble the small arteries in so far 
that their walls may be considered as composed of three coats, 
but each of these coats is of a more or less complex nature, 
and the minor details of their structure differ in different 
arteries. 

It should be observed, however, that as a general rule, 
the muscular fibers in the small arteries bear a larger pro- 
portion to the elastic than to the larger arteries. 

The Capillaries. — If we examine the various tissues of 
the body, we shall find that, with some few exceptions, they 
are traversed with a network of very small tubes (capillaries) 
which surround the elements of the tissues. This is beauti- 
fully shown by the microscopic examination of an injected 
specimen of voluntary muscles 
(Fig. 134) or the web of a 
frog's foot. 

These little tubes, although 
very small, vary in size, from 
that so small that one red cor- 
puscle can with difficulty pass, 
to that in which, three or four 
may pass abreast. The size, 
too, of the capillary will vary 
with blood pressure. 

The walls of the true capil- 
laries are very thin, consisting 
of a single layer of spindle- 
shaped cells cemented together 
so as to form a tube. It is in these small tubes that the work 
of the interchange of the materials between blood and tissues 
takes place. Through these thin walls the blood may give 
to the cells of the tissues the materials they need for their 
nutrition and work, and the cells may give back the waste 




Fig. 134. — Capillaries, Tail op 

Tadpole. 

1. Endothelial cells. 2. Nucleus. 

Notice the joining of the branches 

(anastomosis). (Brinckley 0. W. B.) 



1 The larger arteries are, as a rule, deep-seated, being superficial at only a 
few points, as at the wrist, the temples, the popliteal sp.ice, and the ankle. At 
these points they are so near the surface that their pulsation may be felt. The 
radial artery is generally taken to determine the pulse. The large arteries are 
accompanied by one or more large veins called the venae comites. 



270 THE CIRCULATORY SYSTEM. 

product of its activities as carbon dioxide, etc., to the blood. 

It is in these little tubes and the minute capillaries that 
the great work of the blood takes place. 

The walls of the other blood vessels are too thick for 
the blood to pass through. 

In many parts of the body these little tubes are so 
numerous that the tissues could not be pierced by a needle 
without touching one of them. Coming to these from the 
heart are a system of tubes (arteries), furnishing the chan- 
nels wherein to send a supply of blood to the capillaries. 

Going from them to the heart is another system of vessels 
(veins), furnishing the channels for the drainage of the waste 
products of the cell activities. 

The Veins, — These vary in different parts of the body 
so very widely that it is very difficult to give a general 
description of a structure suitable to all veins. 

It may be said, however, that they differ from the 
arteries in having much thinner walls ; and these walls con- 
taining relatively much more white connective tissue and 
much less yellow elastic tissue, muscular fibers are found 
in a larger or smaller proportion. 

Valves. — Many of the veins are provided with pouch- 
like folds of the inner coat. The mouth of the valve is 
directed from the capillary toward the heart. These are 
so placed that in case of re-flow of the blood, it will be 
stopped by the valve. The onward pressure of the blood by 
means of the valves causes the blood to be lifted against 
gravity. 

The valves are absent in the viscera and in those veins 
in which the blood is not forced to flow against gravity. 
They are therefore found in greatest number in the extrem- 
ities. The more important veins without valves are the venae 
cava?, hepatic, portal, renal, spinal, cerebral, and pulmonary. 

As the arteries divide, their united caliber increases so 
that the channels for the blood flowing from the heart may 
be represented by a funnel (Fig. 132) with wide portion 
direct from the heart. On the other hand, the veins unite 



THE VEINS. 271 

to form larger ones, and the united caliber become less, so 
that they could be represented by a funnel with small por- 
tion direct toward the heart. This increased and decreased 
caliber has a great influence upon the rate of flow of blood in 
different parts of the body. 

It is important to remember that the total capacity of 
the veins far exceeds that of the arteries. Indeed, nearly 
the entire quantity of blood may be forced into the portal 
vein and its brandies. The united sectional area of the cap- 
illaries is about four hundred times that of the aorta. 

The elasticity and the muscular elements of the middle 
coat are very important factors in determining the con- 
stancy of the flow of the blood, and in regulating the blood 
pressure. We have seen that the arteries and veins are 
capable of increasing their caliber. The question might nat- 
urally arise, " Is there any way in which their size may be 
regulated ? " There are times when the heart must do more 
work than at others. Can its beat be so regulated as to enable 
it to do the extra work I The above questions are almost too 
difficult to treat in the present work, but there are a few prin- 
ciples we must know, even to have an elementary knowledge 
of circulation. 

The muscular fibers of the arteries and veins are pro- 
vided with two kinds of nerve fibers {vasomotor nerves) 
(Fig. 135), one causing the contraction of the muscular 
fibers (vaso-constrictors) coming from the spinal cord 
through the sympathetic to the artery ; the other causing the 
relaxation of the muscular fibers (vaso-dilators)\ coming 
from the cranial nerves, and therefore medullated fibers. 
The former decrease the size of the artery, and the latter 
increase it. The heart is also governed by two sets of fibers, 
the inhibitory fibers going by means of the spinal accessory 
from the central nervous system (medullated fibers), and the 
augment ory fibers coming from the anterior roots of the 
second and third dorsal nerves, but which lose their medulla 
before they reach the heart. The stimulus of the one and 
the inhibition of the other could cause an increase in the 



272 THE CIRCULATORY SYSTEM. 

heart's beat. The conditions reversed, the result would be a 
decrease of the heart's beat. 

SYSTEMIC CIRCULATION. 

Arteries. — From the demonstrations which are given in 
this article we may learn that there arises from the left ven- 
tricle of the heart a great arterial trunk, the aorta. At its 
very base are given off two small arteries, coronary arteries 
(Fig. 129), which go to the heart. The aorta soon curves up- 
ward, across, and downward, forming what is called the arch 
of the aorta; from the right and upper part of the arch is 
given a branch {innominate artery), which soon divides into 
two branches, one with its branches supplying the head and 
neck (right common carotid), the other {right subclavian) 
passing onward over the axilla of the arms (here called the 
axillary artery), then onward down the arm (brachial ar- 
tery) ; at the elbow it divides into two branches, one on the 
radial side (radial artery), the other on the ulnar side (ulnar 
artery). From these are given off branches which go to 
the hand. 

From the left and upper part of the arch is given off 
a branch which with its branches goes to the head and neck 
(left common carotid). A short distance to the left is given 
off another branch (left subclavian artery), which goes to 
the arm having the same divisions as the corresponding ar- 
teries on the right side. 

The Aorta now curves downward and backward, keeping 
very close to the spinal column, and after giving off branches 
to the walls of the chest and the organs contained in it, 
passes through the diaphragm into the abdominal cavity. 
Soon there is given off a branch (coeliac axis) which breaks 
up into three divisions, one going to the stomach (gastric 
artery), another to the spleen (splenic artery), and the other 
to the liver (hepatic artery). A short distance below this 
there is given off a large branch which goes to the small 
intestine and to part of the large intestine (superior mesen- 
teric artery). Just below the superior mesenteric a branch 



THE GREAT VEINS. 273 

is o-iven off from the right and left sides of the aorta which 
goes to the kidney of that side {renal artery). About two 
inches above the division of the aorta, from its left side, is 
given off a branch which is distributed to a part of the 
large intestine {inferior mesenteric), ^ear the fourth lum- 
bar vertebra the aorta divides into two great branches (right 
common iliac and left common iliac), and these in turn soon 
divide into two large branches; the inner one (internal iliac) 
going to the pelvic viscera, and the outer (external iliac) 
continuing onward to and down the thigh (femoral artery). 
It then passes downward from the adductor magnus to the 
popliteus (popliteal artery), where it divides into two 
branches, one going to the front of the leg (anterior tibial) 
and the other continuing downward on the back portion (pos- 
terior tibial). From these arteries are given off branches 
which go to the foot. The divisions of the left common iliac 
are like those of the right. 

We should keep in mind the fact that the various arter- 
ies divide and subdivide, and finally break up into capilla- 
ries. We should also remember that we have mentioned but 
a few of the many arteries of the body. 

Veins. — Arising from the capillary network are the 
smaller veins which unite to form the larger ones. On the 
thumb side of the forearm there arises a vein (radial vein), 
which, near the extremity of the forearm above, meets with 
a short branch to form a vein (cephalic vein), which passes 
upward on the outer surface of the arm, and becomes united 
with the subclavian vein. Along the median line of the upper 
surface of the forearm runs another vein, which, near where 
the forearm reaches its greatest diameter, divides into two 
short branches, one going to the right (median cephalic), 
joins the cephalic vein; the other (median basilic) to the left, 
joins the basilic vein. On the side of the little finger arise 
two veins, one on the upper surface (anterior ulnar), and 
the other (posterior ulnar) from the lower surface. These 
unite to form the common ulnar vein, which unites with 
the median basilic to form the basilic. These become 
18 



274 THE CIRCULATORY SYSTEM. 

more deeply seated in the arm, and join with the deep- 
seated veins (brachial veins) which accompany the brachial 
artery, forming the axillary; this passes over the arm- 
pit, and continues onward, passing beneath the clavicle, 
where it changes its name (subclavian vein), and con- 
tinues to near the articulation of the clavicle with the ster- 
num, where it meets a large vein (external jugular) com- 
ing from the head, and forms with it a short vein (left in- 
nominate vein), about an inch and a half in length. The 
right innominate unites with the left to form a large vein 
(superior vena cava), which empties into the right auricle of 
the heart. The divisions of the left innominate are the same 
as those of the right. 

Arising from the branches of the foot is a large vein (in- 
ternal, or long saphenius), which runs along the outer and 
inner surface of the leg and thigh, joining the femoral vein 
near the widest part of the thigh. From the outer and upper 
surfaces of the foot there arises another vein (external, or 
short saphenius), which passes upward along the median line, 
and on the posterior surface of the leg, joins above the knee 
pit with the popliteal vein. More deeply seated will be found 
four large veins, two anterior to the tibia (anterior tibial 
veins). These unite to form a large vein (popliteal vein), 
which extends upivard from the popliteal space of the lower 
third of the thigh, changes name (femoral vein), becomes 
larger by receiving numerous veins when it passes through 
the crural arch (see Gray), where its name is again changed 
(external iliac), and by the union with a branch coming 
from the pelvic viscera it forms a large vein (right common 
iliac), and then, joining with its fellow on the left, forms the 
great venous trunk (^inferior vena cava). From each of the 
kidneys it receives a vein (renal veins), and from the liver 
three veins (hepatic veins). Passing through the diaphragm, 
it empties into the right auricle of the heart. 

In addition to the veins we have mentioned, there is a 
system of veins coming from the digestive viscera, the stom- 
ach, intestines, and spleen ; one from a part of the large intes- 



CIRCULATION OF BLOOD EXPLAINED. 275 

tine (inferior mesenteric) , one from the small intestine and 
a part of the large intestine (superior mesenteric), and one 
from the spleen (splenic vein). By the union of the superior 
mesenteric and the splenic vein is formed a large vein (portal 
vein), which, after receiving veins from the stomach (gastric 
veins), goes to the liver and breaks up into a system of capil- 
laries. The blood is re-collected by the hepatic veins, and 
taken to the inferior vena cava. 

Pulmonic Circulation. — Arising from the right ventricle 
of the heart is an arterial trunk (pulmonary artery), which 
soon divides into two branches, one going to the right lung 
(right pulmonary artery), the other to the left lung (left 
pulmonary artery). These break up into the dense network 
of capillaries of the air cells of the lungs. From these capil- 
laries are formed veins which go to the right to form two 
veins {right pulmonary veins), which in turn go to left auricle 
of the heart; and on the left, two (left pulmonary veins 
which also go to the left auricle. This circulation is called 
the pulmonary circulation, or the lesser circulation. Its 
function is to secure the aeration of the blood. It should be 
kept in mind that the nutrition of the lungs is accomplished 
by another system of vessels, the bronchial veins and arteries, 
which are a part of the systemic circulation. 

Causes of the Circulation of the Blood. — We cannot give 
in an elementary treating of this wonderful and complex 
phenomenon a complete description of why and how the 
blood flows, nor consider the various conditions which modify 
its quantity and force. There are, however, general prin- 
ciples with which we should become acquainted : — 

1. That the great propelling force of the circulation is 
the ventricular contraction of the heart. This force alone is 
sufficient to force the blood from the aorta through arteries, 
capillaries, and veins to the right auricle, or from the pul- 
monary artery to the left auricle. 

2. That the other forces, as resistance offered by the size 
of the capillaries, the muscular coats of the arteries, and the 
veins, the elasticity of the arteries, the pressure due to the 



276 



THE CIRCULATORY SYSTEM. 



contraction of skeletal muscles, in connection with the valves 
of the veins, which prevent a backward flow, the influence 

of respiration, and the force of grav- 
ity, are not causes of circulation, 
but only forces which modify the 
effect of the propelling force of the 
ventricular contraction. 

The great engine which forces 
the blood in its ceaseless round 
through artery, capillary, and vein 
is the heart. 

: ' The rate and the quantity of the 
flow will depend upon the rapidity 
and energy of the heart beat and 
the peripheral resistance. The 
heart's contraction is due to the met- 
abolic changes taking place in the 
heart muscle, and the heart contains 
within itself the stimulus for its 
contraction. In the embryonic heart 
there are no ganglia, and yet the 
heart beats rhythmically ; the heart's 
beat is therefore independent of the 
influence from its ganglia. 

The force and frequency of the 
heart beat is under the influence of 
the central nervous system. The 
stimulus from the two vagi tends to 
lessen the rate of the heart beat (in- 
hibit), while the stimulus from the 
SpuTsSffiwi^SSS'SSS sympathetic nerve tends to increase 
AnnTSuToTvieussens. A £'. ii the frequency of the heart beat (ac- 

and D. 7. The r esp ect i ve t ± \ rri m x j.i 

spinal nerve, c. Sy. Cervical celerate). lhe nbers from the vagi 
sympa e ic. are called the inhibitory nerve, and 

that from the sympathetic system the acceleratory nerve. 
Under normal condition their stimulus is tonic, but if the 
inhibitory stimulus is increased, the heart beat is retarded; 




Fig. 135.— Diagram of Vaso- 
constrictor Fibers of Cer- 
vical Sympathetic and 

Part of the Abdominal 
Splanchnic Nerve. 

Aur. Artery of the ear. G. 
C. S. Superior cervical gan- 
glion. Abd. Spl. Abdominal 
splanchnic. V. M. C. Vaso- 
motor renter in medulla. G. 
Th.\ G. Th.% G. T/i.3, etc. 
The respective thoracic gan- 
glion. Sp. C. The spinal cord. 
The dotted line represents the 
course of the vaso-constrictor 



CIRCULATION OF THE BLOOD. 2< < 

if the accelerator^ stimulus is increased, the force and fre- 
quency of the beat is increased. 

The direction of the flow of excess of blood will be deter- 
mined by the peripheral resistance, and will be toward the 
region of least resistance. The resistance is regulated by the 
muscular coat of the arteries. If the cutaneous arteries are 
contracted, and those of the viscera relaxed, the greater 
amount of blood will flow to the viscera. If, however, those 
of the viscera be contracted, while those of the skin are re- 
laxed, the flow will be from the viscera to the skin. 

The constancy of the flow is due to the peripheral resist- 
ance and the elasticity of the artery walls. 

How the Heart Contracts. — The right auricle during the 
relaxation (diastole) of its muscular fibers, and by the 
fact that all backward pressure from the ventricles is removed 
by the closing of the tricuspid valves, offers but little resist- 
ance to the flow of blood from the veins. The blood in the 
veins is under pressure, which, though diminishing toward 
the heart, remains greater than that within the auricles. As 
a result, the blood flows into the empty auricle, and in case 
of the superior vena cava is assisted by gravity. At each in- 
spiration this flow is favored by the decrease of pressure on 
the heart and great vessels caused by respiratory movements. 
Before this flow has gone very long the relaxation (diastole) 
of the ventricle begins ; the cavity dilates, and the flaps of the 
tricuspid fall back, and the blood for a short time flows in a 
continuous stream into the ventricle. It is not long, however, 
until the ventricle is two thirds full, when a short, sharp con- 
traction (systole) of the auricle completes the filling of the 
ventricle. It will be noticed, however, that the systole begins 
in the great vessels and descends into the heart The force 
of the contraction is spent sending the blood into the ven- 
tricle, where the blood pressure is still less than it is in the 
veins. The ventricle being filled by the auricular systole, the 
systole of the ventricle almost immediately follows. 

Let us keep in mind the fact that the blood in the pul- 
monary artery is under pressure by the tension of the elastic 



273 THE CIRCULATORY SYSTEM. 

arteries, and is pressing upon the semilunar valves as well 
as upon the capillaries and veins. When the ventricles are 
full, the pressure becomes equal on each side of the valves, 
but as the ventricle continues to contract, the pressure from 
the blood in the ventricle becomes greater than that of the 
blood in the arteries, and the blood is sent with a bound into 
the pulmonary artery. So completely is this done that the 
walls of the ventricle come in contact, and all the blood is 
forced out. As soon as the ventricle begins to relax, there 
being no longer pressure from the ventricle, the blood presses 
back upon the semilunar valves, and closes them. During 
the whole of this time the left side has, with still greater 
energy, been executing the same movements. 

Each auricle contracts at the same time, but the contrac- 
tion of the left auricle is stronger than that of the right. 
Close upon the contraction of the auricles follows the systole 
of the ventricles, which, like the auricles, takes place at the 
same time, but the right contracts with much greater force ? 
Why ? 

After the systole of the auricle and ventricle, there is a 
short passive period (the rest of the heart), in which there is 
neither contraction nor relaxation. 

The diastole and systole of the auricles and ventricles, 
and the passive interval, taken together make the car- 
diac cycle, or heart heat, which in a heart beating seventy- 
two times a minute lasts for .08 second. The ventricular 
contraction lasts about .03 second, the passive interval about 
.04 second, .01 of which the auricles and ventricles are relax- 
ing, and .03 second there is neither a contraction nor relax- 
ation, but absolute rest. 

At each contraction of the ventricle there is sent a wave 
along the entire length of the arteries. 

Sounds of the Heart. — If the ear be placed on the chest 
of another person, over the heart region, two sounds will be 
heard during each round of the heart's beat. They are 
known as the first and second sounds of the heart. The 
first is of a lower tone, but of longer duration; the second, 



THE BLOOD. 279 

sharp and quick; they may be imperfectly represented by 
the syllables "lub," "dub." 

The cause of the second sound is the closing of the semi- 
lunar valves. As to the cause of the first there is much 
doubt. Some suppose it to be due to the vibration of the 
tense ventricular vails during a systole, while the more 
recent view is that it is double in its origin, partly due to 
the closure of the semilunar valves. 

These sounds are of importance to the physician, as in 
disease of the heart they are cloaked by other sounds or so 
modified as to become of great aid in determining the diffi- 
culty. 

In health, in the adult, the pulse ranges from sixty-five 
to seventy-five; in children it is faster; in old age, slower, 
and faster again in extreme age. 

A soft pulse j i. e., when the arteries are readily com- 
pressible, shows that the heart is not keeping them properly 
filled; a tense, or hard, pulse indicates that the heart is 
keeping the arteries excessively full, and is working violently. 

How the Valves Adapt Themselves to Variation in Size of 
Auriculo-Ventricular Openings. — The little muscular pillars 
projecting from the walls of the ventricles, from which pass 
tendinous cords, in turn attached to the auriculo-ventricular 
valves, have a very important function. When these valves 
close back after the systole of the auricle, they are prevented 
from swinging too far back by these little tendinous cords ; 
but when the ventricles contract, these little cords become 
slackened, and the valves would be forced up into the auricles 
were it not for the contraction of these little papillary 
muscles, which shorten as the ventricles continue in their 
contraction, and thus keep the chordse stretched, and keep the 
valves from being forced back. 

Rate of Flow.— The velocity of the blood differs very 
much in different parts of its course. It leaves the arteries, 
going from the heart with a bound, and becomes slower and 
slower as it reaches the smaller arteries, and at the capilla- 
ries the movement is almost imperceptible to the unaided 



280 



THE CIRCULATORY SYSTEM. 



eye. As the blood leaves the capillaries, the stream becomes 
quicker in its now, the greatest velocity of the venous now 
being reached in the larger veins. The cause of this differ- 
ence in velocity in the different parts of the circulation, aside 
from the force given by the heart impulse, is purely physical. 
The repeated branching of the arteries increases the surface 
over which the blood Hows, and the greater resistance offered 



[PULSE 




















































1 


140 
130 
120 
110 
100 
90 
8Q 
70 
60 
50 
40 
30 
20 
10 




















































1 






















































t 


















































| 


r 




















































T 






















































v 
































































































































































































































































































































































































































































AGE 


5 10 15 20 25 30 3540 45 50 55 60 65 70 75 80 85 90 95 100 



Fig. 136.— Pulse Curve. 
Numbers at left show pulse; those at the base, age. 

by this increased surface checks the velocity of the flow; 
in the vein the converse is true, the capillaries and smaller 
veins forming larger veins, the surface over which the blood 
flows becomes less, and a corresponding decrease of resist- 
ance follows, and also an increased velocity of the flow. 

Work Done by the Heart. — The heart, forcing as it does 
the blood into the arteries against great pressure, has to do 
a great work. It is estimated that the ventricles do daily 
as much work as would be required to lift 193 tons one foot 
high. 

Why Is There No Pulse in the Capillaries ? — The loss 
of the pulse in the capillaries is due to the following 
facts : — 

1. That from their small size they present considerable 
resistance to the flow due to friction. 

2. To the elasticity of the arteries. 

3. By their great number the shock becomes divided. 



THE BLOOD. 281 

Importance of No Pulse in the Capillaries. — In the cap- 
illaries the interchange between the tissues and the blood 
must take place. If the flow was unsteady or rapid, this 
could not well take place, but the slow, steady stream, 
through these tiny vessels gives ample time for the inter- 
change. 

Taking Cold. — When the skin is chilled, its arteries con- 
tract; this throws an undue amount of blood into the in- 
ternal organs, and they thus become gorged with blood 
(congested), and this congestion very easily passes into in- 
flammation. A continued chilling may pass into a continued 
inflammation, or cold. Diarrhea is more frequently due to 
chill resulting in inflammation of the mucous membrane of 
the intestine than to the fruits eaten to which we usually 
give blame. 

Need of the Blood. — It is not sufficient for the purpose of 
nutrition that the food products enter the blood. It must be 
taken to the various tissues whose cells take the food, and 
make it a part of themselves. 

Small animals, like the one-celled forms found in our 
ponds, the hydra and fresh-water sponge, have no need of 
blood, as they are so simple that the cell or cells which 
make up the animal may absorb food from the medium 
in which they are found; but when they become so com- 
plex as to have organs, the labor of the cells is divided: 
some are concerned in respiration, some in production of 
motion, some with sensation, and some in preparation of 
food. Thus many are far removed from the alimentary 
canal in which the food products are made, and some food 
must be brought to them so that they may be nourished, 
and be supplied with materials needed for the performance 
of their various functions. This is accomplished by the 
blood and circulatory system. Thus it is that the food 
products prepared by the alimentary canal are taken to the 
brain, muscles, bones, and other parts of the body. But 
this is not the only need of blood. The cells need oxygen. 
This the blood gets from the lungs. This also must be 



282 THE CIRCULATORY SYSTEM. 

taken to the cells. The cells in their activities in the pro- 
duction of heat and motion make waste products which are 
of use no longer to the system, but must be thrown off, so 
that we shall have need of currents to and from the cells, 
and an engine to keep up the currents. This is accom- 
plished by the veins, capillaries, and arteries, and by the 
heart as a force pump. The blood is thus the medium of 
exchange between the receiving organs on the one hand (as 




Fig. 137. 
1. Red corpuscles of blood of a duck. 2. Red corpuscles of Wood of snake. 
3. Red corpuscles, blood of rat. 4. Red corpuscles, blood of cat, forming bundles 
(rouleaus) like rolls of coin. 5. Red corpuscles from human blood. Notice 
nucleus in 1 and 2, and its absence in 3, 4, and 5. (Brinckley, C. W. B.) 

the lungs and alimentary canal) and the excretory on the 
other. 

Where Found. — The blood is found in all parts of the 
body with the exception of the epidermis, or outer skin, the 
hair and the nails, most cartilage, and hard parts of the 
teeth. 

Color. — The color of the blood differs in different parts 
of the body ; as it goes to the lungs, it is almost a purple in 
color j as it returns, it is almost a scarlet in hue; and after 



THE BLOOD. ^«^ 

digestion, its color is changed by the absorption of food 
materials. 

Histology. — The blood consists of the plasma and cor- 
puscles. The corpuscles are so small and so numerous that 
over 50,000 are contained in a single drop of blood. The 
red are by far the greater in number. The ratio is about 
one white to three hundred red ones. The plasma is the 
fluid portion of the blood in which the corpuscles float. It 
is almost colorless and quite transparent. 

The composition of plasma may be learned by the exam- 
ination of blood serum, which is plasma minus fibrin. While 
it has the consistency of water, it is not like water in com- 
position. When boiled, it sets like jelly or the white of an 
egg. This would indicate that it is probably like it in 
composition, which is true, there being about eight and one- 
half pounds of albuminous substance to one hundred pounds 
of blood. It also contains considerable quantities of oily 
and fatty matters, a little sugar, common salt, carbonate of 
soda, and small quantities of various other substances, chiefly 
waste products from the various tissues. It is nine-tenths 
water. 

Red Corpuscles (Fig. 137).— When seen separately, they 
are of a pale yellow color, but together they are red, and to 
their color is due the red appearance of the blood. Soon after 
the blood is drawn, the most of the red corpuscles cohere 
side by side, in rows resembling piles of coins. The red 
corpuscles of mammalia resemble those of man, being cir- 
cular, biconcave, pale, yellow disks. The blood corpuscles 
of the dog are so much like those of man that they might 
be mistaken for those of human blood. In most cases 
their size is sufficient to enable us to distinguish them. The 
oval shape, and the presence of a nucleus in the red cor- 
puscles of birds, reptiles, amphibians and fishes, will prevent 
them from being confounded with those of human blood. 
Each corpuscle is soft and jelly-like. It is composed of 
water, phosphorus, iron, potassium, and haemoglobin. Water 
is the chief constituent, being more than half the weight. 



284 THE CIRCULATORY SYSTEM. 

The haemoglobin has power of uniting with oxygen when that 
gas is in excess, and of giving it off again when the oxygen 
is small in amount. In the lungs the haemoglobin takes up 
oxygen. To carry oxygen from the lungs to the various tis- 
sues of the body is one function of the red corpuscles. The 
haemoglobin is dark-purplish red, but when combined with 
oxygen, it is bright-scarlet red. The bright-red blood is 
called arterial, and the dark venous. 

White Corpuscles. — The white blood corpuscles in the 
human body are larger than the red. They contain no color- 
ing matter. Each has a well-marked nucleus, and the power 
to change its own shape. Their' movements are so much like 
those of the amoeba that they are called amoeboid. The pus, 
or matter, of a sore is chiefly made up of white corpuscles 
which have worked their way through the walls of the capr 
illaries. 

The Blood Gases. — Ordinary fresh water has consider- 
able air dissolved in it; this is the source from which the 
fish and aquatic animals derive their oxygen. Blood also 
contains gases 1 dissolved in it. By exposing the blood to a 
vacuum, it gives off about sixty pints of gas to one hundred 
pints of blood. Arterial blood contains more oxygen and less 
carbon dioxide than venous blood ; but, in both, the propor- 
tion of carbon dioxide is greater than that of the oxygen, and 
is the most abundant gas of the blood. 

The Quantity of Blood. — The total weight of the blood 
is about one twelfth or one thirteenth of the weight of the 
whole body, making for a man of average size about twenty 
pounds of blood, or somewhat over a gallon and a half. 

The Specific Gravity of Blood. — Bulk for bulk, blood is 
heavier than water, one hundred teaspoonf uls of blood weigh- 
ing as much as one hundred and five teaspoonfuls of water. 
The blood is much thicker than pure water. Its specific grav- 
ity varies from 1.055 to 1.06, when taken at 15° C. In addi- 
tion to the solid bodies which float in the plasma it holds a 



i The percentage composition of arterial blood is: O, 19.2; 00 2 , 39.5; N, 2.7: 
for venous blood, 0, 11.9; C0 2 , 45.3; N, 2.7. 



COAGULATION OF BLOOD. 285 

number of substances in solution, — things which are of 
great importance, for they are the foods which the blood is 
carrying to, and the waste which it is carrying from, the 
various tissues of the body. 

The Coagulation of Blood. — When first drawn, blood 
flows as freely as water. This condition is only temporary. 
In a few minutes the blood becomes viscid and sticky, resem- 
bling thick, red syrup ; the viscidity becomes more and more 
marked until, after the lapse of five or six minutes, the whole 
mass sets like jelly, adhering to the sides of the vessel so • 
firmly that it may be inverted without being spilled. Gelat- 
in izat ion is the name given to this stage of coagulation. 
This condition, however, is not permanent. In a few min- 
utes the top of the jelly-like mass begins to hollow out, or 
cup, in the hollow of which appears a small quantity of a 
nearly colorless liquid, the blood serum. The jelly mass 
at length shrinks so as to pull itself loose from the sides 
and bottom of the vessel, and as it shrinks, it squeezes out 
more and more serum. At last we get a solid clot, red in 
color, smaller in size than the vessel in which it is contained, 
but retaining its form and floating in a quantity of pale yel- 
low serum. This series of changes is known as coagulation, 
or clotting of the blood. 

Cause of Coagulation. — When a drop of fresh drawn 
blood is watched with a powerful microscope, it will be seen 
to separate into very fine solid threads which run in various 
directions through the plasma, and form a close network en- 
tangling the corpuscles. These threads are composed of an 
albuminous substance called fibrin. When they first form, 
the whole drop is much like a sponge soaked full of water 
(represented by the serum), and having solid bodies (the 
corpuscles) in its cavities. 

After their formation, these threads begin to shorten, 
causing the fibrinous network to shrink in every direction, 
and this shrinking increases, the longer the clotted blood is 
kept. The same thing takes place in the coagulation of the 
blood in quantity. At first they stick too firmly to the sides 



286 THE CIRCULATORY SYSTEM. 

and bottom of the vessel to be pulled away, hence the first 
sign of contraction is seen in the cupping of the surface after 
the stage of gelatinization, and this contraction presses out 
from its meshes the first drops of serum. At last the con- 
traction of the fibrin overcomes the adhesion to the vessel, 
and pulls itself loose from all sides, and it continues to con- 
tract, pressing out more and more serum. Nearly all the red 
corpuscles are held back in the meshes of the fibrin. The 
coagulation is produced by an unformed ferment called 
thrombin, which is not present in the blood of the healthy 
blood vessels, but is formed when the blood is shed. It is 
supposed that the thrombin is produced by the breaking down 
of the white corpuscles, especially the polynuclear. The 
soluble calcium salts of the blood seem to be very important 
factors in producing coagulation. 

Uses of Coagulation. — 1. To clog up wounds in the small 
blood vessels, and thus to stop bleeding. 2. To seal perma- 
nently a ligatured blood vessel. 

Query. — How are such tissues of the body, as the car- 
tilage, the epidermis, hair, and nails, and the hard parts of 
the teeth, nourished, since they are not provided with blood 
vessels ? 

THE LYMPHATIC SYSTEM. 

Part of the plasma of the blood exudes through the thin 
walls of the blood capillaries, thus coming in contact with 
surrounding tissues. This exuded plasma becomes the lymph, 
and contains in solution nutrient material and oxygen set 
free from the red corpuscles of the blood, and thus becomes 
a nutritive and respiratory agent for the cells of the tissue, 
each tissue taking from the lymph what it needs for its life 
and activity. The surplus lymph, together with the waste 
products resulting from the metabolism of the tissue, is 
carried away from the tissues and back to the blood stream 
by a system of vessels called the lymphatics. These vessels 
have their origin in the tissues, and are found in nearly all 
parts of the body. 



THE LYMPHATIC SYSTEM. 



28? 



They are, however, most in- 
timately connected with the 
connective- tissue. The lym- 
phatics include the following 
classes of vessels : (1) lymphat- 
ics proper and the gland which 
belongs to them; (2) the lac- 
teals, which arise from the in- 
testines, and which differ from 
the lymphatics proper only in 
their power to absorb chyle dur- 
ing digestion as well as exuded 
lymph; (3) the serous mem- 
branes which inclose cavities, 
which are in reality large 
lymph spaces, as the pleural 
cavity, synovial membrane, per- 
itoneum, and pericardium. 

The lymph bathes the tis- 
sues, filling up the spaces be- 
tween the cells and other tissue 
elements of the body. Includ- 
ing that found in the tissues 
and contained in the lymph ves- 
sels, its quantity exceeds that 
of the blood-vascular system, and 
forms more than one fourth of 
the weight of the body. Bath- 
ing the tissues as it does, and 
being between them and the 
blood vessels, it acts as a me- 
dium of exchange between the 
blood and the tissues. By the 
lymph the tissues receive their 
oxygen and nutrient materials, 
and into the lymph the tissues 
receive their waste products. 




Fig. 138. — View of the Great 
Lymphatic Trunks. 

1, 2. Thoracic duct. 4. Right lym- 
phatic duct. 5. Lymphatics of the 
thigh. 6. Iliac lymphatics. 7. Lum- 
bar lymphatics. 8. Intercostal lym- 
phatics, a. Superior vena cava. b. 
Left innominate vein. c. Right in- 
nominate vein. d. Aorta, e. Infe- 
rior vena cava. 3. Left subclavian 
vein. 



288 



THE CIRCULATORY SYSTEM. 



Origin and Structure of the Lymphatics. — The lymphat- 
ics begins in most cases as minute channels in the tissues, 
which unite and form tubes resembling the blood capillaries, 
but as a rule the lymph capillaries are larger; these soon 
take upon themselves covering, and resemble the veins, but 
have thinner walls, a larger proportion of muscle fibers in 
the middle coat, and much more numerous valves, giving to 
them a beaded appearance. These collect into larger trunks, 
forming two main trunks, the larger one on the left side, 
known as the left lymphatic duct, or thoracic duct, and 
emptying into the left subclavian vein. The lymph is col- 
lected by these vessels, and carried to the subclavian veins. 
There is thus a constant stream of lymph going from the 

tissues to the 
lymphat- 
ic ducts, and 
b y them t o 
the respective 
subclav- 
ian veins. 

Some o f 
the lymphat- 
ics seem to 
arise by a 
plexus, or 
network of 
tubes, as 

Fig. 139. — Diagrammatic Section of Lymphatic Gland. x 1X 

a. I. Lymph vessels going to (afferent) gland, e. I. Lymph branes, b U t 
vessels going from (efferent) gland. C. Cortical substance. ; 

M. Reticular cords of medulla. 1.8. Lymph sinus, c. Capsule man y ol 
with trabecule, tr. (Sharpey.) J 

these vessels 
commence in irregular {lacunar) spaces in connective tissue, 
(sometimes called lymph spaces), these forming into lymph 
capillaries. The lymph capillaries form a network in various 
organs of the body. Their walls are composed of a single 
layer, endothelial cells. The capillaries form numerous an- 
astomosing branches. In the course of the lymphatic vein 
there are numerous bodies called lymphatic glands. 




THE LYMPHATIC SYSTEM. 289 

In the intestines, lymphatics (here called lacteals) begin 
by blind extremities in the villi (Fig. 119). In the large 
serous cavities, the lymphatics, by free stomata on the walls 
of the cavities, are not, as once supposed, closed cavities, but 
have numerous openings by the stomata, and by the lymph 
lacunae; their fluids are drained away into the lymph cap- 
illaries lying in the subserous tissue. In the central nervous 
system the capillaries have around them for a short distance 
a lymph capillary in the form of a tubular sheath, so that 
the lymph that leaves the blood capillary at once enters this 
tubular sheath, and from this it is carried into the regular 
lymphatic canals. 

It will be seen from what has been given that as the 
lymph comes in direct contact with the tissues, it reaches 
parts of tissues which have no blood vessels, such as the epi- 
thelium of the mucous membrane, the interior cartilage of 
the cornua, and the innermost cells and substances of bone. 

Lymphatic Glands. — These (Fig. 139.) are small, com- 
pact bodies, which occur in the course of the lymphatic ves- 
sels. They vary in size from a hemp seed to a kidney 
bean, and through them pass the lymph and chyle on the 
way to the blood. They are very numerous in the mesentery, 
on the sides of the great vessels of the abdomen, thorax, 
and neck. They are also found in the axilla and groin. 
They are generally of a flattened oval form, with a depres- 
sion at one side, called the hilum, at which the blood vessels 
enter and leave the gland, and where also is the exit for the 
efferent lymphatic vessels. The efferent vessels enter at 
various points of the periphery. 

The lymphatic gland consists (1) of a fibrous envelope 
or capsule made up of a connective and muscular tissue, from 
which there passes inward a framework of partitions (trabec- 
ule) which divides the gland into spaces (alveoli) with 
free communications having the form of converging cham- 
bers in the cortex, but which become less in size and regular- 
ity of shape in the medulla ; ( 2 ) of the glandular substance 
proper, which consists of a mass of lymphoid tissue (a fine 
network of fibers with lymph corpuscles in the meshes), 
19 



290 THE CIRCULATORY SYSTEM. 

occupying the central portions of the spaces, and thus leav- 
ing a narrow channel bridged across by cells and fibers be- 
tween the lymphoid tissue and the trabecule; (3) a free 
supply of blood vessels, the arterial branch running in the 
trabecular framework and breaking in part in capillary net- 
works in the glandular substance; (4) vessels bringing 
lymph to the gland (afferent), and vessels carrying it away 
(efferent). 

In the small portion of the tissue crowded with leuco- 
cytes, active cell multiplication by indirect (karyohinetic) 
division takes place, so it would seem that one function of 
the gland is to produce leucocytes that become the white cor- 
puscles of the blood. There are other localities which contain 
adenoid tissue, as the tonsils, the solitary glands, and Peyer's 
patches, the spleen, etc. 

The lymph which leaves the gland differs from that 
which enters it, in that it is more coagulable, has been freed 
of accidental matter, and is richer in leucocytes. 

The Thoracic Duct.' — This (Fig. 138) is the common 
trunk which receives the lymph from the lower limbs, from 
the abdominal viscera, except the upper portion of the liver, 
from the walls of the abdomen, from the left lung, the left 
side of the heart, left side of the thorax, the left arm, the 
left side of the neck, and head. 

It is from fifteen to eighteen inches long, nearly one-third 
of an inch in diameter, but at its lower portion there is an 
elongated dilation (receptaculum chyli). It extends from 
opposite the second lumbar vertebra to the base of the neck. 
It passes upward along the front of the body of the vertebrae 
by a tortuous course, dilating and contracting at irregular 
intervals, and making a sharp turn, enters the subclavian 
vein near its juncture with the external jugular vein, having 
its entrance into the vein guarded by a valve of two segments 
which permits the contents to pass into the vein, but pre- 
vents any reflux. The valves of the thoracic duct are 
more numerous in its upper portion. The walls of the 
duct consist of three coats: (1) a lining of flattened 
epithelial cells, resting upon longitudinal fibers; (2) a 







SVLV/AN 
FI3SURB 



PLATE XII. 

Fig. 7^. — A Diagram to Illustrate the Probable Functions of 

Various Areas of the Cerebral Cortex. 

(From Ranaey.) 



THE LYMPHATIC SYSTEM. 291 

middle coat of connective tissue, above which there are 
muscular fibers, both longitudinal and transverse; (3) an 
external coat of alveolar tissue with isolated bundles' of mus- 
cular fibers. 

Conditions Affecting the Amount of the Lymph and 
Chyle. — Various causes may combine to determine the 
amount of lymph in the lymphatic spaces and vessels: (1) 
gravity, as is shown by the swollen limbs and tense skin 
when standing for a long time or by letting the arms hang 
at the side and noticing the swollen vessels ; while the swell- 
ing is partly due to the blood capillaries and veins, the greater 
part is due to the unusual fullness of the lymph spaces; (2) 
to pressure, as shown by bandaging the arm, the parts below 
the bandage becoming swollen by the lymph held back by the 
pressure of the bandage; (3) muscular exercise, the exercise 
not only increasing the formation of the lymph, but also 
promoting its more rapid outflow; (4) increase of blood 
pressure in the capillaries, due either to capillary dilation 
or an increased venous resistance or a stronger or more rapid 
heart stroke; (5) the condition of the living cells of the 
capillary wails which may prevent the lymph exudation, as 
in case of conditions given in 4; (6) digestion of a full 
meal; the amount of chyle greatly increases, the lacteals be- 
coming white and distended though collapsed, and contain- 
ing only a small amount of clear lymph during the interval 
between times of digestion; (7) abnormal conditions of the 
vascular system, as lack of tone of capillary walls, may pro- 
duce an excessive transudation of the lymph, with an undue 
accumulation of lymph in the lymph spaces, producing a 
lymph congestion called edema, or dropsy. 

Inflammation. — When part of the tissue of an organ is 
irritated, it leads to an increased flow of blood, as shown by 
rubbing the skin briskly. In such a case the blood vessels 
become dilated and congested, the white corpuscles cling to 
the sides, and begin to pass through the walls of the blood 
vessels into the lymph space. When the irritation is great, 
a morbid condition known as inflammation is produced, char- 
acterized by heat, swelling, and redness, with marked vas- 



292 THE CIRCULATORY SYSTEM!. 

cular changes and much exudation of plasma and corpuscles 
into the injured tissue. 1 When the inflammation subsides, 
the white corpuscles cease to emigrate to the blood, the stream 
quickens, and the normal circulation is again set up; the 
migrated corpuscles and surplus lymph pass away eventually 
into the lymphatic channels. If the inflammation, however, 
continues, a complete arrest of the blood flow may take place ; 
some red as well as some white corpuscles may pass into the 
tissue, and the accumulated leucocytes degenerate into pus 
cells, and form an abscess which must be opened, if it should 
fail to do so naturally. 

THE LYMPH. 

Normal lymph is a clear, transparent, yellowish fluid of 
a specific gravity of from 1.012 to 1.022. It is odorless, 
slightly alkaline, and has a saline taste. Colorless corpuscles 
resembling those of the blood are found in the lymph. Be- 
fore passing through the lymphatic glands, the lymph is only 
slightly coagulable, but after passing through them, and as 
it advances on its course toward the thoracic duct, the num- 
ber of corpuscles increases, and the lymph becomes easily 
coagulated. 

Cause of Circulation of the Lymph. — The more impor- 
tant causes of movements of the lymph are : (1) The pressure 
derived from the blood pressure in the tissue, and by the 
manner of entering the two lymphatic trunks there is little 
or no pressure when they enter the blood vessels. This dif- 
ference of pressure produces an outward flow from the tissues 
to the openings of the lymphatic ducts into the blood vessels ; 
(2) by the arrangement of valves, every pressure on the ves- 

i If the irritation is caused by the lesion of tissue or the presence of foreign 
bodies, as bacteria or other micro-organisms, there is set up an active emigration 
of the leucocytes to the injured part, and these devitalize or engulf and digest the 
disintegrated tissue or foreign particles, and thus prepare the way for repair of 
the tissue. The corpuscles which combat the irritating agent are called phagocytes . 
If the phagocytes are strong or numerous enough to devour and remove the irri- 
tating substances, they disappear by being carried off into the lymph stream ;--but 
if the invading substance is too powerful, the corpuscles themselves are de- 
stroyed, and collected in the tissue and pus cells. The destruction of the in- 
jurious agent is supposed to be a chemical one, the source of the destructive 
agents, the invading or irritating influence, being produced by the chemical 
activity of the cells. 



THE LYMPHATIC SYSTEM. 293 

sels by the skeletal muscles in contraction tends to force the 
lymph onward, and the valves prevent its backward flow; (3) 
the respiratory movements by every inspiration diminish the 
pressure in the vessels within the chest; (4) probably 
the muscular fibers in the lymphatics undergo a rhythmic 
contraction; (5) the lymph (chyle) of the lacteals is forced 
onward by the intestinal movements and the contraction of 
the muscular fibers of the villi; (6) by the union of the 
lymph vessels into larger trunks, but whose sectional area 
is less than that of the total area of the tubes forming the 
trunk. There is thus a constant stream of lymph from the 
tissues to the two subclavian veins, and thus to the blood. 

Uses of the Lymph.— The uses of the lymph are many, 
the more important of which may be mentioned: (1) It 
bathes the tissues, and acts as a medium of exchange between 
the cells and the cell elements of the tissue and the blood. 
The method by which this exchange is made is something 
more than simple osmosis. In addition to the process of 
osmosis there is probably filtration, the lymph passing 
through the tissue under pressure. It also is greatly influ- 
enced by the activity of the endothelial cells of the capillary 
wall. The fact that one half of the indiffusible proteids 
of blood plasma pass into lymph shows that it is something 
more than osmosis; that it is not due to filtration alone is 
shown by the fact that increased pressure is not always fol- 
lowed by increased lymph exudation, and also by the fact 
that waste products often pass from the lymph spaces to the 
blood. When peptone is injected into the blood circulation 
of a living animal, there is produced an increased flow of 
thicker lymph, a more concentrated plasma passing through 
capillary walls, the peptone also passing and disappearing in 
the lymph. This would seem to imply an active process of 
secretion by the cells of the capillary wall; (2) to remove 
waste products that have been formed by the activity of 
tissue, which may not reach the blood by osmosis; (3) as 
a circulating medium between the tissues and the blood ; (4) 
as absorbent vessels gathering matter and passing it to the 
blood. 



CHAPTER X. 

RESPIRATION. 
EXPERIMENTS AND DEMONSTRATIONS. 

I. To determine the structure of the lung: Obtain from 
the butcher a calf's or a hog's lung. It is best to get one 
with the heart attached, as in removing the heart, holes are 
likely to be cut which will interfere with the inflating of 
the lungs. In dissecting note carefully : — 

1. Shape and size of the larynx, and position of the 
glottis and epiglottis. 

2. Relation, shape, size, and structure of the trachea. 

3. Color, size, shape, specific gravity, and relation of 
the lungs to the heart, etc. 

4. Trace out the larger blood vessels connected with the 
lungs and heart. 

5. Carefully slit open the trachea on its posterior; care- 
fully examine its inner surface. Do you find any glands ? 
Determine the structure and shape, form and number of 
the rings. Do you note any difference in their size ? Trace 
the rings to the bronchi. 

6. Carefully trace out the division of the bronchus as 
far as you can. 

7. Carefully cut off the left lung at the beginning of the 
left bronchus. 

II. Tie into the left bronchus a few inches of glass tubing 
of convenient size ; tie very firmly. On the end of the tube, 
tie a few inches of rubber tubing. On blowing into the tube, 
the lung will be distended, and as soon as the opening is left 
free it will collapse. What does this show of the structure 
of the lungs ? 

Now carefully inflate the lung as completely as possible, 
and while inflated; firmly tie the rubber tube, about two 
inches from the glass tube, so that the air cannot escape. 
294 



EXPERIMENTS AND DEMONSTRATIONS. 295 

Take a U-shaped tube one-fourth inch in diameter, and with 
arms eighteen inches long. Pour mercury into the tube until 
it stands about four inches in each arm. Tie the free end 
of the rubber tube connected with the inflated lung to one 
arm of the U-shaped tube. Cut the string that confines the 
air in the lung, and gradually admit the air into the tube. 
Does the mercury rise in the opposite arm \ Why ? How 
much ? Find the difference in level. Try the same experi- 
ment with an inflated rubber balloon. 

III. Dissect out and identify the muscles mentioned 
below. 

1. Carefully determine the structure and relations of 
the diaphragm. 

2. Dissect out the serratus, and determine its action as 
an inspiratory muscle. Do the same for the pectoralis major 
and minor and scaleni. 

IV. To show that elasticity of the lung aids in expiration, 
make a piece of apparatus as follows: Into the lid of the 
ordinary self-sealer glass fruit jar have soldered two tin tubes 
about one-fourth inch in diameter; one near the center and 
the other near the edge. Let the one near the edge project 
below the surface of the top two inches, and above one and 
a half inches ; to the one in the center tie a rubber balloon so 
that it can be inflated by blowing into the tube above. To 
the outer one connect a rubber tube of sufficient length and 
size, and then connect with an air pump. Now exhaust the 
air from the jar, and notice any change that may take place 
in the balloon. Give reason for the change. Admit the air 
to the jar. Explain what takes place. In what way does 
this resemble the manner in which we breathe ? 

Queries. — 1. Why is it that as soon as the air is admitted 
to the pleural cavity the lungs collapse ? 

2. What difference would be made in our mode of breath- 
ing if the lungs were not elastic ? 

3. By what force are the lungs stretched ? What princi- 
ple of physics is involved ? Give reason for your answer. 

•i. Why does the expansion of the lungs keep up with 
that of the chest wall ? Is there a vacuum or partial vacuum 



296 RESPIRATION. 

produced as in the jar apparatus ? Give reason for your 
answer. 

5. What muscles should be brought into action to pro- 
duce artificial respiration? Determine by careful examina- 
tion of the muscles of a cat. 

EXPERIMENTS. 

1. To Determine Force of Expiration : Make a U-shaped 
one-fourth-inch glass tube having even arms about eighteen 
inches in length and two inches apart. Support the tube so 
it can stand vertical. Into one arm pour mercury (quick- 
silver) until it stands on a level in both arms, about four 
inches high; to one arm attach a piece of rubber tubing. 
Into the free end of the rubber tubing insert a piece of glass 
tubing two or three inches long, leaving about an inch and 
a half out of the tube. Now blow through the tube, and see 
to what height you can raise the mercury in the opposite 
arm. Let a number of persons try the experiment. Compute 
the weight of the mercury you lift. Try the force of suction 
by taking a deep, forced inspiration. What effect upon the 
relative heights of the columns ? Why is the result opposite 
that of the first experiment ? What important principle 
does it teach ? Compute the difference between the expira- 
tory and inspiratory efforts. Determine the average inspir- 
atory and expiratory efforts. 

2. To Determine the Vital Capacity : Take a larger bell- 
jar, and fill it full of water ; now invert it into a pneumatic 
trough partly filled with water so that when the water is 
forced out of the jar the water in the trough will not over- 
flow. Support the bell-jar by a string and pulley and weight 
so that it will be balanced. 

Take a piece of rubber tubing about a yard long. In 
one end of the tubing insert a piece of glass tubing about 
four inches long, so that about two inches will remain out 
of the tube. Place the end with the glass tube in the 
mouth and the other end of the tube under the bell-jar, so 
that it will reach up some distance in the jar. Without tak- 
ing more than an ordinary inspiration, force the water out 
of the jar by an ordinary expiration. Mark the distance 
to which the water falls. Take as deep an inspiration as 
possible, and after filling the jar with water expel it as much 
as possible by as great an expiratory effort as you can make. 



EXPERIMENTS AND DEMONSTRATIONS. 297 

Again mark the point to which the water falls. Now with- 
out removing the tube from the mouth, make an inspira- 
tion. Does the water rise in the jar? Why? Let a num- 
ber of persons try the experiment, and note carefully in 
each case the fall of the water. After the first experiment 
remove the jar from the water, and determine the amount 
of water (in quarts) required to fill it up to the first mark. 
Then round the edges of the glass tubing, so that by holding 
the end in the Bunsen or alcohol flame they will not cut the 
mouth. 

3. Take a glass or beaker full of lime water. 1 By means 
of a piece of glass tubing, eight or ten inches long, breathe 
into the lime water, and continue breathing until a white 
precipitate is formed. What is the cause of the precipitate ? 

Place several small pieces of marble in a small flask or 
a large test-tube with a cork having a delivery tube. Add 
some dilute acid, and quickly cork and place the end of the 
delivery tube into a beaker or glass of lime water. Do you 
get a precipitate ? Is it like the one you got in the first part 
of the experiment ? Marble is a carbonate of lime, and 
when an acid is added to it, carbon dioxide is given off, 
which, joining with the lime water, makes calcium carbon- 
ate, which is insoluble. Where did the carbon dioxide of 
the breath come from ? What have we learned is one of the 
chief waste products in muscular contractions ? 

4. Turn down a Bunsen burner until there is only a small 
flame, and place over it a four-inch or five-inch funnel having 
a delivery tube running from the small part of the funnel 
into a glass of lime water. Is a precipitate formed ? What 
is formed by the burning of the gas ? If the carbon of the 
gas joins with the oxygen of the air, what will be formed ? 
What use do the tissues make of the oxygen ? 

5. Place on a wooden float a piece of candle. Light the 
candle, and place in a pneumatic trough or bucket of water. 
Cover with a bell-jar or a large fruit jar. Why does the 
candle go out? Leaving the mouth of the jar closed by the 
water, remove the float. Close the mouth of the glass jar 
with a glass square or piece of wood; invert the jar quickly, 

i Lime water may be made by adding unslacked lime to pure water until it 
will no longer dissolve. Set the solution aside for a few hours, and then filter, 
saving the clear water that passes through the filter. Keep in well-corked 
bottles. 



298 RESPIRATION. 

and remove the jar from the pneumatic trough. Remove 
the cover, and put in 10 or 20 c.c. of lime water; put on 'the 
cover, and shake the jar to secure the mixing of the gas 
and lime water. Does the lime water become milky, or is 
there a precipitate formed ? What does this indicate ? 

Repeat the experiment, but admit air by means of two 
bent glass tubes or by two rubber tubes. Does the candle 
continue to burn ? Why ? Test as before with lime water. 
Do you get so marked a test for carbon dioxide as in the 
first case? What do you learn in this experiment of the 
effect of carbon dioxide upon combustion ? Why do we use 
two tubes ? 

If the chemical changes which take place in the cells are 
oxidations, would carbon dioxide, if not removed by the 
tissue, tend to prevent this oxidation? Why do the tissues 
need oxygen ? 

In a closed room how does respiration of the persons in 
the room render the air unfit for rebreathing ? How may the 
injurious effects be prevented ? 

6. If 1,200 cubic inches of air is rendered unfit for 
breathing by one person in breathing one minute, what vol- 
ume of air will be required to last 100 persons one hour ? 

7. A schoolroom is 30 feet by 60 feet by 12 feet ; how 
long will this amount of air last 30 pupils if 1,200 cubic 
inches is required per minute for each pupil? How much 
air must be supplied each minute to keep the air fit for 
breathing ? 

8. By what has been given, test the air supply of your 
sleeping room. 

THE RESPIRATION. TEXT. 

Need. — As a result of the activity of the cells of the 
various tissues of the body, there is produced, directly or in- 
directly, through a series of decompositions, carbon dioxide. 
This is the most abundant of the waste products. While it 
is a normal product of the cells' work, its presence in any 
large amount in the blood or in the tissues is injurious to 
the activity and health of the tissue. It must be removed 
from the tissue by the blood, and then from the blood before 
it returns to the tissue. 

Many of the chemical processes which take place in the 



RESPIRATORY APPARATUS. 299 

cell are dependent upon a gas which is plentiful in the air ; 
i. e., oxygen. There are also a number of products from 
digestion which have been absorbed by the blood, whose en- 
ergy cannot be set free without the aid of oxygen. There is 
constant demand for this material, and therefore a constant 
supply must be kept up. 

Kespiration has for its objects (1) to renew the supply 
of oxygen in the blood, and (2) to get rid of the carbon 
dioxide. 

As this work is so different from any we have considered, 
and as we have learned that new functions require new 
organs or modification of organs, we shall expect to find a 
separate set of organs to perform this work. Not only do 
we find this, but when we extend our observations to the 
lower animals, we learn this very important truth. The 
more extended the work of oxidation is to be, the more com- 
plex and better developed is the respiratory apparatus, and 
the more thoroughly the blood is aerated ; i. e., charged with 
oxygen. 

Respiratory Apparatus. — The respiratory tract consists 
of the air passages and the lungs. These consist of the nose 
opening into the pharynx by the posterior nares; of the 
mouth opening into the same cavity by the fauces; of the 
pharynx opening on its ventral side by a slit (the glottis) 
into the larynx ; of the larynx opening below into the trachea ; 
of the trachea, which divides into two great branches, or 
bronchi ; of the bronchi, which divide into a large number of 
smaller tubes, and these finally after many subdivisions open 
into subdivided elastic sacs with pouched walls. 

We shall not at this time describe the nose, nasal fossae, 
larynx; the pharynx was described when we considered ali- 
mentation ; the others will be described when we consider the 
voice and the sense of smell, respectively. 

We should, however, in this connection, note the posi- 
tion of the larynx (Fig. 140a), surmounting the trachea, and 
in front of the pharynx ; that it is a triangular box made up 
of nine cartilages, three single and three pairs, bound to- 



300 RESPIRATION. 

gether by ligaments, and moved by numerous muscles; and 
that the interior is lined by mucous membrane, is supplied 
with blood vessels and nerves, and contains the vocal cords. 

The Trachea. — The trachea (Fig. 140a) extends from the 
larynx to the bronchi; its length is about four and a half 
inches, and its diameter about three fourths of an inch. It is 
a cylindrical tube lined by mucous membrane, with a sup- 
porting stratum of connective tissue and plain muscular tis- 
sue. The wall contains from sixteen to twenty cartilages 
which have the form of imperfect rings, and extend about 
two-thirds the way round the trachea. The third not sup- 
ported by the rings rests upon the esophagus. 

The bronchi and bronchial tubes are very similar in struc- 
ture to the trachea ; these rings, like those of the trachea, are 
only partial rings, but are so placed that they give support 
to the entire circumference of the tube by not having the 
partial ring with their openings at the same place. 

The Cilia of the Air Passages. — The greater portion of 
the mucous membrane of the nose, the nasal fossa, the phar- 
ynx, down to the opening of the posterior nares and that of 
the trachea and its branches, down to almost the smallest, 
have a layer of ciliated cells on its surface. Each of these 
cells has on its free portion, which is turned toward the cavity 
of the tube, from twenty to thirty slender threads which are 
in constant motion. These little thread-like bodies are called 
cilia. This motion serves a very important function which 
will be described later. 

Lungs. — The lungs (Figs. 5 and 140a) are suspended in 
the chest by the root of the lungs, consisting of the pulmonary 
arteries and veins, bronchial arteries and veins, lymphatics, 
bronchial tubes, and areolar tissues, all inclosed by reflection 
of the pleura. 

The lung is composed of an external serous (pleura) 
coat, a subserous coat containing a large proportion of elastic 
fibers, and the parenchyma. The parenchyma is composed 
of lobules which vary in size ; those of the surface are large 
and of pyramidal form; those of the interior, smaller, and 



THE LUNGS. 



301 



of various forms. Each lobule is composed of one of the 
ramifications of the bronchial tube and its terminal air cells, 
and of the ramifications of the pulmonary and bronchial ves- 
sels, lymphatics, and nerves, all of these structures being 
connected together by areolar fibrous tissue. 

The bronchial tubes (Fig. 140) become smaller and 
smaller 
by c o n - 
tinued d i - 
vision until 
they are 
from one 
fiftieth t o 
one t h i r - 
tieth of an 
inch, when 
they become 
changed i n 
s t r u c - 
ture, losing 
their cylin- 
drical form 
and contin- 
uing on- 
ward as ir- 
regular pas- 
sages (air 

sacs) through the substance of the lobule, their sides and ex- 
tremities being closely covered by numerous saccular dila- 
tations, the air cells. 

The Air Cells. — The air cells are small, polyhedral, cup- 
shaped depressions separated from each other by thin septa, 
and communicating freely with the intercellular passages, or 
air sacs. They are best seen in the surface of the lungs; 
they vary in size from one two hundredth to one seventieth 
of an inch. The important changes to be noticed in the 
structure of the air cells are the loss of muscular fibers, 




Fig. 140 A.— Organs or Respiration. 
1. Left lung. 2. Right lung. 5. Larynx. 7. Trachea. 9. Left 
bronchus. 14,15,16. Bronchial tubes. 



302 



RESPIRATION. 



the extreme thinness of the mucous membrane, the abundance 
of elastic fibers, and the change from columnar ciliated cells 
to pavement epithelium. 

Pulmonary Capillaries. — These are found just beneath 
the mucous membrane in the walls of the septa of the air 

cells and the air sacs : their 



walls are very thin, and 
they form plexuses having 
very minute meshes. 

Pleura. — Each lung is 
invested on its external 
surface by a very delicate 
serous membrane (the 
pleura), which incloses the 
organ as far as its root, and 
is then reflected upon the 
inner surface of the 
thorax. The cavity be- 
tween these two layers is 
called the cavity of the 
pleura. Each pleura is a 
closed sac, one occupying 
the right half of the 
thorax, and the other, the 
left. The two pleurae do 
not meet in the middle of 

3. the chest, excepting oppo- 
site the upper part of the 

There is a space (the medias- 




Fig. 140 B.— Structure of Lungs. 
1. Bronchial tube. 2. Bronchiole. 
Infundibulum. 4. Alveolus. 



second piece of the sternum 

tinum) thus left between the two, which contains all the 

viscera of the thorax except the lungs. 

The Diaphragm — This, it will be remembered, is the 
muscular membrane which divides the ventral cavity into 
two parts, the thorax and abdomen. It is made of two mus- 
cles (diaphragm major and diaphragm minor). The first 
originates by fleshy slips from the lower portion of the ster- 
num (ensiform appendage) and from the inner surface of 



THE DIAPHRAGM. 



303 



the cartilage of the last six ribs. Converging by all its fibers 
to a broad central tendon, it is inserted into a tendon which 
is notched in shape at the vertebral column, and pointed near 
the sternum (the cordiform tendon). There is an opening 
(foramen quadrat um) near the spine through which the vena 
cava ascends. The second originates by four pairs of fleshy 




Fig. 141. — The Diaphragm. Interior Surtace. 

1. Foramen for vena cava. 2- Onening for the esophagus. 3. Central ten- 
don. L Psoas minor muscle. 5. Psoas major. 6. Quadratus lumborum. 7. Open- 
ing for the aorta and the thorac duct. 8. Right crus. 9. Median arch. 10. 
Lateral arch. 11. Lateral crus made from 9 and 10. 



and tendinous slips, the longest of which arises from the 
third and fourth lumbar vertebra? ; the second from the liga- 
ment between the second and third lumbar vertebra?; the 
third pair from the sides of the second ; and the fourth pair 
from the base of the transverse process of the same vertebra?. 
It passes by muscular bands upward into two columns, one 
on each side, and is inserted into the back and notch of the 
cordiform tendon. In this muscle there are two openings, 
one (esophageal) through which passes the esophagus and 



304 RESPIRATION. 

pneumogastric nerve; through the other (hiatus aorticus) 
the aorta, thoracic duct, and the greater splanchnic nerve. 

Respiration consists of two acts, inspiration and expira- 
tion. The former is an active effort even in ordinary breath- 
ing, while the latter is a passive one. They both, however, 
become active efforts in forced respiration. "When we notice 
the movements of the chest during normal breathing, it is 
seen that during inspiration the chest becomes enlarged in its 
diameter from before backward, the sternum being thrown 
forward and upward (Fig. 1Q0). The lateral width of the 
chest is also increased. 

In a woman the movement of the upper part of the chest 
is often conspicuous, the chest rising and falling at every 
respiration; in a man, however, the movements are almost 
entirely confined to the lower part of the chest, showing that 
they are diaphragmic. 

In labored respiration all parts of the chest are alter- 
nately expanded and contracted, the chest rising and falling 
as much in a man as in a woman. 

Inspiration. — There are two chief means by which the 
chest is enlarged in normal inspiration, — the descent of the 
diaphragm and the elevation of the ribs. The former causes 
that movement of the lower part of the chest and abdomen 
seen in a man's breathing and called diaphragmic; the latter 
causes the movement of the upper part of the chest seen in 
women's respiration, and hence is called costal. It should be 
remembered that even in the respiration of a woman the 
diaphragm takes an important part, while in a man the 
diaphragm is the chief respiratory agent. The descent of 
the diaphragm is effected by means of the contraction of its 
muscular fibers. When at rest, it presents a convex surface 
to the thorax ; when contracted, it becomes much flatter, and 
in consequence the level of the chest is lowered. In descend- 
ing, the diaphragm presses on the abdominal viscera, and so 
causes a projection of the flaccid abdominal walls. The 
elevation of the ribs, however, is a more complex movement. 

Since all the ribs have a downward slanting direction, 



MECHANICS OF BREATHING. 305 

they must all tend, when raised toward the horizontal posi- 
tion to thrust the sternum forward; some more than others, 
according to their slope and length. The elasticity of the 
sternum and costal cartilages, assisted by the articulation of 
the sternum to the clavicle above, permits the front surface of 
the chest to be thus thrust forward as well as upward when 
the ribs are raised. By this the diameter from before back- 
ward is enlarged. The elevation of the ribs increases not 
only the diameter from before backward, but also from side 
to side. 

The ribs are raised by the contraction of certain muscles. 
Of these the external intercostal are perhaps the most impor- 
tant, being assisted by the scaleni. Next in importance are 
the levatores costarum. Some deny, however, that either set 
of intercostals takes any important part in raising the ribs. 
They think the only use of their contraction is to render the 
intercostal space firm and the whole thoracic cage rigid, so 
that the thorax is moved as a whole by the other muscles men- 
tioned. 

labored Inspiration. — When respiration becomes labored, 
other muscles are brought into action, the number of the mus- 
cles concerned and the degree of their contraction varying 
with the demands of respiration. Among the more important 
may be mentioned the serratus posticus superior, elevating 
the second, third, fourth, and fifth ribs. 

In forced respiration the lower false ribs, not very notice- 
able in easy breathing, come into play. They are depressed, 
retracted, and fixed by giving increased support to the dia- 
phragm and directing the whole energy of that muscle to the 
vertical enlargement of the chest. The serratus posticus in- 
ferior, by depressing and fixing the last four ribs, acts as an 
aid in respiration. • When, however, the need for greater in- 
spiratory effort becomes urgent, all the muscles, which can 
form any fixed act in enlarging of the chest, come into play. 
In this way the serratus magnus acts on the first eight or 
nine ribs; the pectoralis minor acts on the third, fourth, 
and fifth ribs, the pectoralis major from the second to the 
20 



306 RESPIRATION. 

sixth ; the latissimus dorsi on the last three ribs ; all of these 
serve to elevate the ribs, and thus enlarge the chest. Every 
muscle, which by its contraction can either elevate the ribs 
or contribute to the fixed support of muscles which do elevate 
the ribs, may in great efforts be brought into play. 

Expiration. — In normal, easy breathing, expiration is, 
in the main, simple, the effect of elastic reaction. By the 
effort of inspiration the elastic tissue of the lungs is put on 
a stretch. Being thus on a tension, as soon as the muscles 
of inspiration begin to relax, the elasticity of the lungs comes 
into play, and drives out a portion of the air contained in 
them. The elasticity of the sternum and -costal cartilages 
causes them to return to their former position, thus depress- 
ing the ribs and lessening the dimensions of the chest. When 
the diaphragm descends by pushing down the abdominal vis- 
cera, it puts the abdominal walls on the stretch, and hence 
when the diaphragm begins to relax after an inspiration, 
the abdominal walls return to their place, and by pressing 
upon the abdominal viscera, push the diaphragm up again 
to its position of rest. While expiration during easy breath- 
ing is principally an elastic reaction, there is probably some, 
though in most cases, a very slight, muscular action to 
bring the chest more rapidly to its former condition. This 
is supposed by many to be effected by the internal intercostal 
acting as depressor of the ribs. The contraction of the 
abdominal muscles probably assists in the return of the 
abdominal wall ; also the triangularis sterni by pulling down 
the costal cartilages. 

Labored Expiration. — In this act the abdominal muscles 
become important expiratory agents. By pressing on the 
contents of the abdomen they thrust them, and therefore the 
diaphragm also, up toward the chest, the vertical diameter 
of which is thereby lessened; while by pulling down the 
sternum and middle and lower ribs they lessen also the cavity 
of the chest. They are in fact the principal expiratory mus- 
cles. They are probably assisted by the serratus posticus 
inferior and portions of the sarco-lumbalis. When expira- 



METHODS OF BREATHING. 



307 



tion becomes more and more labored, every muscle in the 
body, which by contraction either depresses the ribs or presses 
upon the abdominal viscera or affords support to muscles 
having this function, is called into play. 

How Respiration Takes Place — The lungs are placed in a 
state which is always one of distention, varying in degree; as 
the chest enlarges, they, together with the heart, great blood 
vessels, and other organs, completely fill the air-tight thorax. 
The enlargement of the lungs consists chiefly in an en- 
largement or expansion of the pulmonary alveoli, the air in 
which becomes, by expansion, rarefied. This makes the pres- 
sure of the air within the lungs less than that outside them, 
and this difference of pressure causes a rush of air through 
the air passages into the lungs until an equilibrium is estab- 
lished between the air inside and that outside. This consti- 
tutes an inspiration. When, by the relaxation of the inspir- 
atory muscles and elasticity of the lungs and chest walls, 
aided perhaps to some extent by the contraction of certain 
muscles, the chest returns to its former size, the pressure 
within the lungs becomes greater (by the air in the reduced 
alveolus becoming compressed) than that of the air outside. 
The air moves out as air flows in from the high to the low 
pressure. This continues until the pressure within the lungs 
and that without is in equilibrium. This constitutes an 
expiration. 

The fresh air introduced into the upper part of the pul- 
monary passages, by inspiration, contains more oxygen than 
the lower part of the lungs. By diffusion, the new, or tidal, 
air gives up its oxygen to, and takes carbon dioxide from, 
the old or stationary air, aud thus when it leaves the chest 
in expiration, it has been the means of both introducing 
oxygen into the lungs and removing carbon dioxide. It is 
in this way, by the ebb and flow of tidal air, and by diffusion 
between it and the stationary air, that the whole air in the 
lungs is being constantly renewed. 

In ordinary respiration the expansion of the chest never 
reaches its maximum by mere forcible muscular contraction, 



308 RESPIRATION. 

and additional thoracic expansion is produced, causing an 
inrush of a certain additional quantity of air to restore the 
equilibrium. This additional quantity over that of ordinary 
respiration is called complemental air. 

In forced respiration the cavity of the chest is then re- 
duced, and an additional amount of air forced out; the 
amount thus forced out, over that of ordinary respiration, is 
called reserve or supplemental air. But even with strongest 
forced expiration there is still some air in the lungs. This 
is called residual air. 

The total amount of air that can be given out by the 
most forced expiration following the most forcible inspira- 
tion, that is, the sum of the complemental, tidal, and supple- 
mental air, is called the vital capacity. Although the amount 
varies largely, yet from 200 to 250 cubic inches would repre- 
sent the average. Of the whole measure of the vital capacity, 
about thirty cubic inches is an average of the tidal air, the 
remainder being nearly equally divided between the com- 
plemental and reserved air. The amount left in the lungs 
after the deepest expiration averages from eighty-four to 
one hundred and twenty cubic inches. 

Changes of the Air in Respiration. — During the stay in 
the lungs, or rather its stay in the bronchial passages, the tidal 
air (chiefly by diffusion) effects exchange with the station- 
ary air, and as a result, the expired air differs from inspired 
air in several particulars. 

1. Temperature. — The temperature of expired air is vari- 
able, but under ordinary circumstances, is higher than that 
of inspired air. The expired air takes its temperature from 
that of the body, which is usually higher, but it may at times 
be lower than that of the atmosphere. The temperature of 
the inspired air depends (1) on the relative temperature of 
the blood and the inspired air, and (2) on the depth and rate 
of breathing. The change of temperature does not take 
place in the lungs, but in the upper passages and chiefly in 
the nose and pharynx. 



CHARACTER OF EXPIRED AIR. 309 

2. Amount of Water. — The expired air is loaded with 
water vapor. The amount of moisture taken up by the ex- 
pired air depends (1) upon the relative humidity of the 
inspired air; (2) upon the temperature of the inspired air, 
the amount increasing with the rise of temperature. The 
moisture, like the warmth, is imparted not in the lungs, but 
in the upper air passages. The inspired air is, therefore, as 
it passes into the bronchi, already saturated with moisture. 

3. Amount of Oxygen The expired air contains about 

four or five per cent less oxygen, and about four per cent 
more carbon dioxide than inspired air, the quantity of 
nitrogen suffering little change. The amount of nitrogen 
in expired air is sometimes greater than in inspired air; 
it sometimes equals it, and is sometimes less. 

In a single breath the air is richer in carbon dioxide and 
poorer in oxygen at the end of the breath than at the begin- 
ning, hence the longer the breath is held, that is, the greater 
the pause between inspiration and expiration, the richer the 
expired air will be in carbon dioxide. 

The quantity of oxygen used, and carbon dioxide given 
ofT, is subject to very wide variations even in the same in- 
dividual. 

4. Impurities Besides the carbon dioxide and mois- 
ture, the expired air contains various impurities, many of 
which are of an unknown nature, and in all small quanti- 
ties traces of ammonia have been found. The water vapor 
found in the expired air contains organic matter, which, from 
the micro-organisms introduced in the inspired air, is very 
likely to putrefy, many products of which are poisonous. 
The bad odor of the breath is often due to the presence of 
these products. Air containing one per cent of carbon diox- 
ide from breathing is highly injurious, even if the air should 
contain only .08 per cent of carbon dioxide from breathing, 
is unwholesome, not so much from the carbon, as from 
the accompanying impurities. To keep the percentage of 
carbon dioxide at one per cent, an average man should be 
supplied with at least 120,000 liters of air per hour. 



310 RESPIRATION. 

Need of Ventilation. — If a person were placed in an air- 
tight room, it would not be long until he would become poi- 
soned by his own breath. When the per cent of carbon diox- 
ide reaches more than one per cent of the air, the air is 
unfit for respiration. As 2,000 liters of air are rendered 
unfit for breathing in one minute, it will not take long to 
render the air of the room unfit for breathing. The supply 
of fresh air must equal the amount rendered impure if the 
air is to be kept fit for breathing. This can only be 
had by ventilation. When the percentage of carbon dioxide 
in the air is equal to, or greater than, that of the blood, the 
blood returns to the heart unchanged and to the tissues 
unpurified, returns to the heart more heavily laden with 
carbon dioxide, and finally becomes so impure that the heart 
ceases to beat under its poisoning influence, and death by 
asphyxia is the result. 

Importance of Deep Breathing. — Lung capacity has been 
very appropriately called the " vital capacity." Every cell is 
dependent upon oxygen for its proper activity. The lungs 
are the source of the supply of this important element. Good 
lung capacity gives endurance and health to the body. 

The lungs, like other organs of the body, need exercise 
to reach their best development; if this is not given by the 
employment in which we are engaged it must be supplied by 
exercises in breathing. 

Avoid all positions and modes of dress which interfere 
with the proper development of the lungs. If you have good 
lungs, keep them so by frequent deep breathing; if weak 
lungs, strengthen them by special attention to daily exercises 
in deep breathing. 

Breathe Through the Nose. — This is important: (1) to 
remove the dust from the air inspired by the action of the 
cilia of the mucous membrane of the air passages; (2) to 
bring the air more nearly to the temperature of body, by its 
passage through the nasal fossae; (3) to give moisture to 
the air inspired by its passage over the upper part of the air 
passage. Very dry air would be irritating to the delicate 
lining membrane of the lungs. 



EFFECTS OF SMOKING. 311 

One of the evil effects from smoking comes from the 
irritating effect of the dry smoke. 

If the air be too cool, it tends to congest the mucous 
membrane of the lungs, resulting in a cold, inflammation, 
or pneumonia. 

In running we should be very careful to observe this rule, 
as the increased volume of air inspired increases the danger 
of congestion to the lungs. 



CHAPTER XL 

METABOLISM. 

FOODS. 

As we have seen, the body is a machine for the transfor- 
mation of energy. This energy must come from onr food, 
and is needed (1) to produce animal heat; (2) muscular 
contraction (motion) ; (3) to carry on the work of the nerv- 
ous system (sensation and stimuli) ; (4) for the work of the 
special senses. If the body is to keep its vigor and power, 
this energy must be maintained; if it is to increase its 
power and size, it must have energy in excess of that needed 
for its present requirements. 

How much food is needed? This is a vital question, 
but its answer involves many difficulties. We do not know 
the secret process by which the food is transformed into tis- 
sue or its energy is set free to produce life, motion, heat, 
and sensation; and we are equally ignorant of the physical 
and chemical properties of the substance (protoplasm) by 
which these changes are produced. How, then, is our ques- 
tion to be answered. 

Every engineer has a similar problem to solve. He is 
to maintain the speed of the train, and keep up the proper 
heat for the warming of the cars for the comfort of the pas- 
sengers. The source of the needed energy is in the coal, 
water, and air. His problem is, How much water, how 
much coal, how much air are needed to keep up the fire and 
steam pressure ? A like problem presents itself in our great 
heating plants, and here we see it answered in a scientific 
way. The weight of the coal used is determined ; the amount 
of water used, measured ; the number of heat units produced, 
estimated; the ashes are weighed, and the loss by smoke 
computed. Thus by knowing the wastes, the available en- 
313 



INCOME AND OUTGO OF THE BODY. 313 

ergy produced, and the amount of fuel used, the value of 
given fuel can be determined, and the amount needed to 
maintain a given temperature in the buildings to be heated. 
By a similar method we may determine the amount of food 
and oxygen needed for the body. 

By carefully estimating the amount of food and air taken 
in the body (the ingesta), and determining the waste prod- 
ucts of the undigested parts of the food, we may learn the 
nature and quantity of the energy produced and the food 
value of any article of diet. 

The substances taken (ingesta) are food and the inhaled 
oxygen. The waste and cast-off products are urine, fseces, 
sweat, and expired air, and a small amount by the sebum, 
cast-off epithelium, hair, etc. 

The more important elements of the income and outgo of 
the body are nitrogen, carbon, and oxygen, and, by estimat- 
ing these, we may approximate the nature and quantity of 
the metabolism of the body. 

Carbon Equilibrium. — If as much carbon is taken up as 
is given off, the body is said to be in carbon equilibrium; 
i. e., the amount taken and the amount consumed are equal. 
If more carbon is taken up than is given off, the body stores 
up the organic matter ; but if the amount given off is greater 
than that taken, part of the organic substance is being lost. 

The proportion between the carbon dioxide exhaled and 
oxygen inhaled gives us the means of determining how much 
of the inhaled oxygen is used to oxidize the carbon, 1 and how 
much is used to oxidize other elements, especially hydrogen. 
The proportion between the carbon dioxide exhaled and the 
oxygen inhaled is called the respiratory quotient, 

Proteids and fats do not contain enough oxygen to oxi- 
dize their hydrogen; they will, therefore, need oxygen both 
for their carbon and part of their hydrogen, so that the 
amount of carbon dioxide will be less than the oxygen in- 

i Carbohydrates contain enough oxygen to oxidize all the hydrogen (the pro- 
portion of typical carbohydrates being hydrogen 2 and oxygen 1), so that oxygen 
inspired goes to oxidize the carbon. The oxidized hydrogen will be given off as 
water (H 2 0), and that of the carbon as carbon dioxide (C0 2 ). 



314 METABOLISM. 

haled. When pure carbon is oxidized, the resulting volume 
of carbon dioxide is the same as the oxygen consumed, and 
in such a case the respiratory quotient is said to be one. 

If the part of the oxygen inhaled is used to oxidize the 
hydrogen or any other element, the carbon dioxide exhaled 
will be less than the oxygen inhaled, and the respiratory 
quotient will be less than one. 

The respiratory quotient can be greater than one when 
the carbon dioxide exhaled is greater than the oxygen in- 
haled. This can be the case when, in the body, carbohy- 
drates, which are rich in oxygen, are reduced to products con- 
taining less oxygen, as in the formation of fats. From what 
has been said it will be seen that in the case of oxidation 
of fats in the body the respiratory quotient will be less than 
one, as the fats have not enough oxygen to oxidize their 
carbon and hydrogen. Compare the composition of the fats 
and carbohydrates in the following table : — 

Carbohydrates. Fats. 

Glucose, C 6 H 12 6 Palmitin, C 51 H 98 6 

Maltose, C 12 H 22 lt Stearin, C 57 H 110 6 

Cane Sugar, C 12 H 22 O xl Olein, C 57 H 104 6 

Notice that the carbohydrates contain enough oxygen to 
oxidize the hydrogen so that all the inhaled oxygen can be 
used to oxidize the carbon. How is it in case of the fats, 
if one oxygen atom is required to oxidize two hydrogen atoms 
to form one molecule of water (H 2 0) ? 

Nitrogen Equilibrium. — Proteid metabolism may be esti- 
mated by determining the amount of nitrogen 1 in the nitro- 
gen wastes (urea, etc. ) of the body. If the amount of pro- 
teids decomposed in the body is equal to the proteids taken 
up, the body is said to be in nitrogen equilibrium. If more 
nitrogen is taken up by the body, there is an increase of the 

i As the proportion of the nitrogen to the carbon in proteids is 1 to 3.3 (by 
•weight), for every gram of nitrogen appearing in the waste products, there will 
be 3.3 grains of carbon oxidized, and a corresponding amount of carbon dioxide. 
By estimating the amount of carbon dioxide due to proteid oxidation as shown 
by the nitrogen consumed, and taking this amount from the total output of 
carbon dioxide, we may determine how much of the carbon dioxide is due to the 
oxidation of carbohydrates and fats, and thus determine the nature and 
quantity of the metabolism taking place. 



FOODS. 315 

proteid material, and hence an increase of flesh. If the 
body gives off more nitrogen than is taken up, there will be 
a loss of proteid material. 

Problems. — 1. From the following data 1 determine the 
condition of the nitrogen and the carbon equilibrium : — 

Income (food and oxygen) 3480 grams containing 321 C, 21 N, 30 Salts. 

Outgo (various excretions) 3342 " 280 C, 21 N, 20 Salts. 

Difference, +~138 +HC 

1. Is carbon stored up ? 

2. In the present case the volume of the oxygen inhaled 
was 503 liters and the carbon dioxide exhaled 464 liters. 

From the formula, E. Q. = v ° J Q % determine the res- 
piratory quotient. 

3. Does the answer of 2 show that the carbon was 
stored up as fat, proteids, or carbohydrates ? 

How Metabolism Is Modified. — The metabolism of the 
body is subject to various changes, both in degree and kind. 
The more important conditions are the body at rest, the body 
at work, the quantity and composition of the food, climatic 
conditions, weight of the body, age, and sex. 

CHARACTER OF FOOD REQUIRED. 

The Quantity of Food. — If there be no food taken, as in 
starvation {inanition), the vital processes go on very much 
the same except in degree. In the first stages the carbon 
dioxide exhaled decreases, but during the latter part there 
is but a slight decrease. At first the proteids decrease very 
rapidly; i. e., the amount consumed until it is less than one 
half, when it remains constant until a short time before death. 

The oxygen taken up during starvation is not so great 
as in normal conditions, but not so small as the decrease in 
the amount of carbon dioxide. 

There is less carbon consumed and more hydrogen than 
in normal metabolism. 

During starvation there is a loss of body weight, a less 
vigorous and rapid heart beat, general weakness, but a uni- 



i Data taken from Schenk and Giirber's Human Physiology (Henry Holt 
and Co). 



316 METABOLISM. 

form normal body temperature, except just before death 
when the temperature falls rapidly. 

According to Volt's analyses the percentage loss of each 
organ from starvation is as follows: fat, 97; spleen, 66.7; 
liver, 53.7; muscles, 30.5; blood, 27; kidney, 25.9; skin, 
20.6; intestines, 18; lungs, 17.7; pancreas, 17; bone, 13.9; 
nervous system, 3.2; and heart, 2.6. 

Starvation may result from insufficient food as well as 
from the absence of food, the time of death due to complete 
starvation being only delayed in the former case. 

1. Lack of Water. — Lack of water will produce death 
sooner than a lack of solid foods. While water takes no part 
in the chemical changes, it is essential to the consistency of 
the tissues and the circulating fluids of the body. 

2. Deficiency of Salt. — If the food is wanting in the 
various salts needed by the body, the excretion of salts 
steadily decreases, and that of common salt soon ceases al- 
together, but that of calcium and sodium phosphates contin- 
ues. As we have seen, a certain proportion of these salts are 
essential to the life processes. Death finally results from 
weakness and paralysis. 

3. Lack of Organic Food. — If only water and salts are 
given, the body consumes itself as in complete absence of 
food, producing the same phenomena, but causing a slight 
delay in the time of death. 

4. Lack of Proteids. — ■ If food containing the proper 
amount of water, salts, fats, and carbohydrates be taken reg- 
ularly, as in normal diet; or if these be increased, still, if 
proteids are lacking or insufficient, the body loses weight, 
and death results from slow starvation, but coming later. 
Fats and carbohydrates cannot protect the body from the loss 
of proteids. 

If the amount of fats and carbohydrates be large, there 
may be an increase in the fat stored up in the body even 
when there is a loss in the proteids. Increase of body weight 
does not always indicate an improved or healthy condition of 
the body, as it may result from an abnormal carbohydrate 




PLATE XIII. 
How the Food Gets to the Tissues. 
(From Yaggy's "Anatomical Study.") 
Fig. 127— 1. The stomach. 2. The intestines. 3. The liver. 4. The heart. 
5. The Lungs. 6. Gastric vein. 7. Inferior mesenteric vein. 8. Superior 
mesenteric vein. 9. Portal vein. 10. Capillaries of portal vein. 11. Hepatic 
vein. 12. Ascending vena cava. 13- Rijrht auricle of the heart. 17. Mesenteric 
gland. 18. Lacteal. 19. Thoracic duct. 20. Arch of thoracic duct emptying into 
Jeft subclavian vein. 21. Left subclavian vein. 22. Internal jugular vein. 23. 
Left innominata. 24. Descending vena cava. 14. Right ventricle. 16. Pulmonary 
artery. 4S. Left pulmonary artery, whose branches break up into capillaries 
ofthelungs. 50. Left pulmonary vein emptying into left auricle. 15. Leftven- 
tricle. 25. Aorta. 26. Ripht innominate artery. 27. Right subclavian artery. 
28. Brachial artery. 29. Ulnar artery. 30. Radial artery. 31. Carotid artery 
(risht). 32. Abdominal aorta 33. Hepatic artery . 34. Gastric artery. 35. Kid- 
ney. 36. Renal artery. 37. Mesenteric artery. 38. Common iliac. 39. Femoral. 
40. Branches of femoral artery. 41. Branches forming iliac vein. 44. Ascend- 
ing vena cava. 45. Cephalic vein. 43. Brachial vein. 



CHARACTER OF FOOD REQUIRED. 317 

and fat metabolism even when the nitrogen nutrition is below 
the normal. 

5. Lack of Fats and Carbohydrates — While these cannot 
replace proteids, they may in case of some animals (most 
carnivora) be replaced by proteids. This, however, is not the 
case with man, as he cannot digest enough proteids to fur- 
nish the extra amount of carbon and hydrogen to take the 
place of the carbohydrates and fats. Without these an ex- 
cessive proteid diet leads to emaciation rather than to a gain 
of flesh or strength. 

6. The Proper Proportion of Proteids. — As we have seen, 
if the amount of proteids taken is equal to the amount used 
by the metabolism of the body, the nitrogen metabolism is 
kept up. If, however, the amount of proteid taken be greater 
than that used up by the body, there will be an increase 
of the body weight; but this increase of body weight will 
call for an increase of proteids to be taken, as the amount of 
proteids required by the body is proportional to the weight, 
and the nitrogen equilibrium will again be restored. This 
consumption soon reaches a limit, as a point is reached when 
the digestive organs are not able to digest the amount neces- 
sary to furnish the needed material. 

7. The Proper Proportion of Fats and Carbohydrates. — 
While these cannot take the place of the proteids, when the 
proteids are wanting in the food, yet, when the body is in 
nitrogen and carbon equilibrium, they may be increased in 
amount ; they may decrease the amount of proteid consumed 
by the body, and if the normal diet is kept up, proteids may 
be stored up by the body. They thus shield the proteids by 
securing a more economical metabolism. 

Effect of Work on Metabolism. — As we have seen, mus- 
cular work increases the respiration and circulation; this 
causes an increase of the consumption of oxygen, and thereby 
the increase of the respiratory quotient and all the processes 
of combustion. In moderate exercise the respiratory quo- 
tient is the same as during rest. In excessive work the excre- 
tion of the carbon dioxide is greater than the oxygen inhaled. 



318 METABOLISM. 

Except where the diet is largely or entirely proteid, the 
excretion of nitrogen is not increased by exercise, and it 
would seem that the metabolism is due to the oxidation of 
the fats and carbohydrates. If the exercise is excessive, there 
will be an increase of nitrogen, even if the food contains 
the proper proportion of proteids. 

In the work of digestion there is an increased metabolism, 
and as the excretion of urea is increased, it would seem that 
the proteids furnish the energy for this process rather than 
the carbohydrates or fats. 

Effect of Climatic Conditions. — As the body must main- 
tain a somewhat constant heat, an increase of external tem- 
perature tends to lessen the heat metabolism, and a lower tem- 
perature tends to increase 1 heat metabolism, and, as the car- 
bohydrates and fats are the chief source of the heat energy, 
their metabolism is increased or decreased with the rise and 
fall of external temperature ; i. e., within certain limits. 

Effect of Size of the Body, Age, and Sex. — If the surface 
by which heat is lost be increased, there must be a corre- 
sponding increase of heat production. In a small person 
there is relatively more surface by which heat is lost than in 
a large one, hence the need of the greater metabolism on 
the part of the smaller person. Sex of itself seems to have 
no effect on metabolism. 

From a careful study of the principles stated we may 
deduce the following principles to govern us in the choice 
and amount of our food: 

1. For the adult man the quantity of food needed is: 
Proteids, 100 grams ; fats, 60 grams ; and carbohydrates, 400 
grams. For the adult woman: Proteids, 90 grams; fat, 40 
grams; and carbohydrates, 350 grams. These amounts are 
required per day. 

2. In the working man the amount per day should be: 
Proteids, 130 grams; fats, 100 grams; and carbohydrates, 
500 grams. 



i"The increase of metabolism during loss of heat is caused by a reflex 
Increase in combustion in the muscles, which produces muscular contraction, 
(shivering)." — Schenck and Giirber's Outlines of Physiology, page 175. 



CHARACTER OF FOOD REQUIRED. 319 

3. That flesh can only be increased by proteid food, but 
while this is true, the body is best nourished by a moderate 
amount of proteids and a large amount of fats and carbohy- 
drates. Exercise favors the laying up of flesh. 

4. For the increase of fat, carbohydrates and fats must 
make up a large proportion of the food. 

5. That a mixed diet is best, and that while the body may 
be nourished by strictly vegetable diet, there is no objection 
to the use of animal food. Animal foods are better absorbed. 
The best diet is a proper proportion of each. 

6. Each of the three classes of food has its distinct use. 
A large amount of carbohydrates and a small amount of pro- 
teids diminish the amount of proteid required to maintain 
nitrogen equilibrium. If the proteids are increased, the 
proteid x metabolism is also increased, and although there is 
a good proportion of the carbohydrates, part of the fat is used 
up to secure the metabolism of the proteids, and thus the body 
loses weight. In a continued excess of carbohydrates in our 
food there is an increase of fat, which results in obesity, 
interfering with the proper nutrition of the muscles, pro- 
ducing feebleness of the heart and other troubles. 

7. The quantity and kinds of food should be adapted to 
the following conditions : — 

a. Climate. — Very slight change is necessary. Eor warm 
climates there should be a slight increase in the amount of 
carbohydrates, the food more easily digestible, and a larger 
proportion of fruits. Eor cold climates somewhat more con- 
centrated foods. 



i " Circulating Proteids." — By this term is meant those proteid substances 
which are dissolved in the blood, lymph, and serous fluids, and by the blood and 
lymph that are continually circulating through the tissues. They furnish the 
material for the replacing of the proteid wastes of the tissue. 

According to Voit, but one per cent of the organic albumin (of the tissue) is 
present in the body, while seventy per cent of the circulating albumin is trans- 
ferred in twenty-four hours." 

"Under ordinary conditions only a small amount of the organic albumin, 
1. e., that composing the tissue, undergoes decomposition, while, owing to the 
action of the cellular elements of the tissues, a large amount of the circulating 
albumin is split up, so that under ordinary conditions the organic albumin is 
comparatively stable." By the stability of the organic albumin is meant that 
while the cells effect the oxidation of the circulating albumin, and thus set 
energy free, the cell substance is little affected, and that the greater part of the 
energy of the proteid metabolism comes from the circulating albumin (proteid) ; 
hence, if this is not present in the blood in sufficient quantities to keep up the 
proteid metabolism, the proteids of the cells must furnish the needed material 
to keep up the metabolism, and thus the body must live upon its own tissue. 



320 METABOLISM. 

b. Hard Labor. — The increased metabolism demands an 
increase of all classes of foods making up the diet. Not so 
great attention is necessary to be given to the digestibility of 
the food, owing to the increased vigor given to the body. 

c. For the Production of Flesh.- — The proportion of the 
proteids should be increased, but with a good proportion of 
carbohydrates and fats. For the best results gentle exercise 
is necessary. In training, the entire diet should be increased, 
as in that for hard labor. 

d. For Brain Work. — In this it is not so much a differ- 
ence in quantity and quality as it is in digestibility. Hard 
muscular labor gives to the body a vigor which is shared by 
the digestive organs, enabling them to digest foods when the 
body is engaged in vigorous work which could not be digested 
when the body is more passive. Brain work, like muscular 
work, makes a heavy drain upon nerve force, and demands a 
large supply of energy ; in the former there is not the accom- 
panying vigorous circulation and respiration which give 
vigor to the entire system; but a passive action of these 
functions, which lessens the vigor of digestive organs, and 
demands, therefore, food more easily digested, but possessing 
high nutritive value. 

e. The Person. 1 — In the selection of food the individual 
is a very important factor, as the amount and kind of the 
food will be modified by his weight, size, activity of certain 
organs, and temperament. 

Diet Tables.- — Various experiments have been made to 
determine the quantity and proportion of the different classes 
of food in a normal diet, and from these, various diet tables 
have been made out. Of these the following from Kirk's 
Physiology will serve to give an idea of the more important 
features of a normal diet : — 



i While the child does not require so much food as an adult, he requires more 
food in proportion to the weight of the body, as there is greater metabolism 
required to support the growing, as well as the more active metabolism required 
to support the body heat. The following is required per one kilogram weight of 
the body : — 

Age. Proteids. Fat. Carbohydrates. 

2-6 years 3.7grms. 3.0grms. 10.0 grms. 

7-15 years 2.8 " 1.5 " 9-0 

Adult 1.6 " .8 '« 8.0 " 

(From Schenck and Gui'ber, Henry Holt & Co.) 



CHARACTER OP FOOD REQUIRED. 



321 



MOLESCIIOTT DIET SCALE. 



Dry Food. 
Proteid, 

Fat, 



120 grms. 
90 ■' 



•Carbohydrates, 320 



(4.232 oz.) supplying 18.80 grms. 
(3.174 " ) 
(11.64 " ) 



a 

64.18 grms. 
70.20 " 
146.82 " 



N. 18.80 



C. 281.20 



Salts, 
Water, 



30 

2S00 



(1.05 oz.) 
(2.95 qts.) 



PETTEXKOFF.R AND VOIT S DIET SCALE. 



Proteids, 

Fats, 

Carbohydrates, 
Salts, 
Water, 



118 to 137 grms. 

56 to 117 " 

352 to 500 ■' 

40 " 

2016 " 



( 4.1 to 4.8 oz.) 

( 1.9 to 4.0 " ) 

(12.1 to 17.0 " ) 

(1.4 " ) 

(2.13 qts.) 



The composition of our more common foods may be 
learned by a study of the following table compiled from 



various sources : 



PERCENTAGE COMPOSITION OF COMMON FOODS. 





Proteids 


Fats 


Carbohy- 
drates 


Water 


Salts 


Cellulose 


I. Animal Food. 


20.5 

9.8 

24.8 

18.1 

21.0 

17.5 

3.5 

12.5 

33.5 

0.3 

11.0 
8.0 

12.6 

10.0 
5.0 
2.0 

24.5 
1.8 
0.5 


3.5 
48.9 
38.5 
2.9 
3.S 
0.5 
4.0 
12.0 
24.3 
91.0 

2.0 
1.5 

5.6 

6.7 

0.8 

0.16 

2.0 

5.0 


.9 

4.0 

70.3 
49.0 
63.0 
64.5 
83.2 
21.0 
52.0 
5.8 
10.0 
96.5 


75.0 
39.0 
27.8 
78.0 
74.0 
80.0 
87.0 
73.5 
36.8 
6.0 

15.0 
40.0 
15.0 
13.5 
10.0 
74.0 
12.5 
91.0 
85.0 
0.3 


1.6 
2.3 
10.1 
1.0 
1.2 
1.5 
0.7 
1.0 
5.4 
2.1 

1.7 
1.2 
3.0 
1.4 
0.5 
1.0 
3.5 
0.7 
0.5 
0.5 




Fat pork 

Smoked ham 

Whitefish 








Cow's milk 




Eggs 




Butter 




II. VegetableFoods 
Wheat flour (white) 
Wheat Dread 


0.3 

0.3 
1 6 




1 5 


Rice 


4 


Potatoes 


1 




6 


Cabbage 


1.5 


Fruit 


4 











Problems. — 1. From what has been given determine if the 
following would be the proper daily diet for a person twelve 
years of age ; potatoes, GO grams ; eggs, 10 grams ; lean beef, 
100 grams; wheat bread (white), 60 grams; butter, 1 gram; 
fruit, 10 grains ; and water, 2,000 grams. Would the above 
be a good diet for an adult engaged in hard manual labor? 
If not, what modification should be made ? 
21 



322 METABOLISM. 

2. Make out a daily bill of fare for a child of ten years. 

3. Make out a daily bill of fare for an adult student. 

4. Determine the relative value of 100 grams of rice and 
100 grams of fat beef (stearin). 

5. If an adult person eats 85 grams of butter, how 
many grams of wheat bread are required to keep up the car- 
bon equilibrium? 

6. If a laboring man eats 350 grams of wheat bread 
(white), 10 grams of fruit, 50 grams of eggs, how much 
lean beef will be required to keep up the nitrogen equilib- 
rium? 



The amount of carbon or hydrogen in a substance may be determined as 
in the following example : How much carbon is there in 50 grams of grape sugar ? 
The formula for grape sugar is C 6 H 12 O e (see page 316). First find the molecular 
weight; viz.: — 

C 6 = 12 atomic weight X 6 = 72 
H 12 = l " " X12 = 12 

O e = 16 " " X 6 = 96 

Molecular weight 180 

Second, determine the percentage*of carbon by proportion; viz., (1) for 0, it 
would be 180 (moleculariweight) : 72 (weight of the carbon) : : 100 (the base of 
comparison) : per cent of O (40 per cent in this case) required; (2) for H it would 
be 180 (molecular weight) : 12 (weight of the hydrogen) : : 100 (base of com- 
parison) : per cent (6.6 in this case) H required, one third the number of grams of 
carbon or hydrogen; viz,: (1) for the O it is 100 (base) : 40 (per cent) : : 50 grams 
(weight of the sugar) : number of grams of O (in this case 20) required; (2) for 
H it is 100 (base) : 6.6 (per cent) : : 50 grams (weight of sugar) : number of grams 
of H (in this case 3.3) required. 

The amount of hydrogen and carbon in^the fat may be determined by the 
same method. 

2 The amount of nitrogen in a proteid may be determined by dividing the 
weight of the proteid by 6.5, and conversely the amount of proteid may be 
determined by multiplying the weight of the nitrogen by 6.5. 



CHAPTER XII. 

ANIMAL HEAT. 

EXPERIMENTS AND DEMONSTRATIONS. 

1. Over a lighted alcohol lamp support an inverted fun- 
nel so that it will collect the gases resulting from the burn- 
ing of the alcohol, and connect the tube of the funnel with 
a glass of lime water so that the gases collected will pass 
into the water. Does the lime water change color, and is 
there a precipitate formed? Is carbon dioxide formed by 
the burning of the alcohol? Do drops of water collect on 
any part of the funnel? Alcohol (ethyl alcohol) has the 
formula of C 2 H 6 O, and if to one molecule of alcohol there 
be added six atoms of oxygen, can you account for the for- 
mation of the carbon dioxide (C0 2 ) and water (H 2 0) ? 

2. Prepare two fruit jars of dry chlorine 1 gas. In the 
first jar drop a piece of cotton soaked with spirits of turpen- 
tine; note the combustion that takes place. In the second 
jar sprinkle some finely powdered antimony. Notice the 
results. In each case the heat is produced by chemical 
change, but in the latter case it is not oxidation, but the 
vigorous union of the chlorine and antimony. 

3. Fit a 250 c.c. flask with a two-holed cork. Through 
one of the holes pass a thistle tube so that it will just reach 
the bottom of the flask, and in the other hole insert a jet- 
tube bent at an obtuse angle (about 140°), so that the jet 
points outward from the thistle tube. Place in the flask 20 

i Chlorine gas may be made in the following manner: place in a flask, 
fitted with a rubber cork and a rubber delivery tube, 20 grams of black oxide of 
manganese {manganese dioxide) and 80 c.c. of strong muriatic acid {hydrochloric 
acid) ; connect the delivery tube with one arm of a U-shaped calcium chloride 
tube (which should be half full of pieces of calcium chloride), and from the 
other arm of the U tube run a rubber tube into the mouth of a quart fruit jar, 
letting the tube go to the bottom of the jar. See that all the connections are 
tight. Heat the flask gently. The chlorine gas being heavier, will displace the 
air. The chlorine gas may be told by its greenish yellow color. Avoid breathing 
the chlorine. As you remove the jars of chlorine as they are filled, which may be 
told by the yellowish green gas, cover them with squares of cardboard or glass. 
Four or five jars will be enough for the experiment. 

323 



324 ANIMAL HEAT. 

grams of granulated zinc; cover it with water to the depth 
of three centimeters. Cork the flask, and see that the end 
of the thistle tube is below the water in the flask. Add 
sulphuric acid gradually through the thistle tube until there 
is a brisk effervescence of the water. Feel the bottom of 
the flask from time to time as you add the acid to see if 
there is any increase of temperature. When the apparatus 
has been working freely for a few minutes, light the jet. 
If the effervescence lessens, add more acid. Hold over the 
jet an inverted tumbler or small bell- jar. What is it that 
collects in drops on the side of the glass? If the gas 
formed in the flask is hydrogen, and the gas joining with it 
is oxygen from the air, can you explain the formation of 
the water on the sides of the glass ? What causes the flask 
to get warm on the addition of the acid to the water? 

The burning of the hydrogen is a case of oxidation, but 
the product is not carbon dioxide, but water. The chem- 
ist represents the action thus : H 2 -+- O = Ha O. 

Two atoms of hydrogen + one atom of oxygen = one 
molecule of water. 

What would the combustion of the hydrogen in the body 
form ? Where would the oxygen come from ? Suppose the 
glycogen of the muscles should be completely oxidized, it 
having the formula of C 6 H 10 O 5 . If it oxidizes into C0 2 
and H 2 0, does it contain enough oxygen to join with the 
hydrogen? How many atoms of oxygen will be needed to 
use up the C ? 

Have fats enough O to use up the H they contain, if 
they have the formula of C 5 ^H 104 O 6 , remembering every 
C will require two O for the formation of C0 3 , and every 
two H one O to form H 2 ? Which make the greatest drain 
on the oxygen of the blood, fats or carbohydrates ? 

4. By means of a glass tube or wheat straw breathe into 
a glass of lime water. What evidence have you that the 
breath contains carbon dioxide ? Where did the carbon diox- 
ide come from? What change does this indicate is taking 
place in the tissues ? 

5. Pour fifteen or twenty drops of ether in the palm of 
the hand, holding the hand so that you will not breathe the 
ether, and notice the cooling sensation produced by the 
evaporation of the ether. Try in the same way some alcohol. 
What difference do you notice? What effect has the rate 



EXPERIMENTS. 325 

of evaporation on the degree of cold produced ? Would 
water evaporating rapidly from the surface of the skin pro- 
duce a similar effect as the ether and alcohol? 

G. When the water in the teakettle is boiling rapidly, 
remove the kettle from the stove, and at once place the hand 
on the bottom of the kettle. Notice that the bottom of the 
kettle is not very warm. As long as the water boils there 
is no danger of burning the hand. Notice that when the 
water ceases to boil the kettle begins to get warmer. How 
do you explain the fact that the bottom of the kettle is not 
hot while the water boils, but becomes so as soon as the boil- 
ing ceases ?' 

In passing from the liquid condition to steam the water 
passes into gaseous condition; to do this heat is required, 
which it takes from the kettle which readily gives up its heat. 

How does a breeze of fanning cool the body ? 

7. If you do not have in the apparatus of the school a 
clinical thermometer, borrow one of a physician, and make 
the following observations : — 

a. Determine your own temperature by placing the bulb 
of the thermometer under the tongue ; keep it in the mouth 
for a few minutes, and then notice the temperature. 

b. Determine your temperature by placing the bulb of 
the thermometer in the armpit {axilla). 

c. Take your temperature immediately on rising in the 
morning; just after breakfast; just before dinner, and one 
or two hours after dinner ; just before retiring at night. 

d. Take your temperature when in a warm room ; when 
out in the cold. 

e. Take your temperature while at rest, then engage in 
some vigorous exercises until you begin to perspire, and 
again determine your temperature. Do you notice any rise 
in the last case ? Let several persons try these experiments, 
and compare results. 

8. Put 50 c.c. (about 40 grams) of 95-per-cent alcohol 
in an alcohol lamp. Place 500 c.c. of ice water in a flask, 
and heat the flask by means of the alcohol lamp for ten min- 
utes. Take the temperature of the water. Determine how 
many grams of alcohol have been used in warming the water. 
Determine by the following formula the calories of heat pro- 
duced by the combustion of the alcohol : — 

500 c. c. of water at 0°C. x temp, of water at close of exper. _ number of calories# 



326 



ANIMAL HEAT. 



This will be approximately true if the water does not boil. 
Each gram of absolutely pure alcohol will give 220 calories 
of heat. 

9. Problems: a. How many calories of heat will 20 
grams of sugar give when completely oxidized, on the fol- 
lowing basis: 1 gram hydrogen on burning yields 34 cal- 
ories ; 1 gram carbon, 8 calories ? 

b. Which will yield the more heat, 10 grams of fat (1 
gram fat = 9.3 calories) or 25 grams of sugar (1 gram = 
3.7 calories) ? 

ANIMAL HEAT. TEXT. 

Need of Heat to the Body. — We have been considering 
the various metabolic processes of the body, and have learned 
that these may consist of those by which tissue is formed and 
of those in which energy is set free for muscular motion, 
nerve force, and heat. In the constructive processes (an- 
abolism) heat is absorbed, but in the destructive processes 
(katabolism) heat is set free. Heat is needed to make up 
for the loss due to constructive metabolism. Heat is also 
needed to maintain the proper temperature for the various 
metabolic processes, as without this temperature these changes 
will not take place. The body is constantly losing heat by 
radiation, and it is in a medium which is sometimes of a 
lower and sometimes of a higher temperature than itself ; it, 
therefore, needs heat to make up for the loss by radiation, 
and also some means of adapting itself to the changeable 
temperature of its surroundings. 

Sources of the Heat of the Body. — The heat of the body 
is due to various destructive metabolic processes, which for 
the greater part are of the nature of oxidation, in which the 
carbon and hydrogen of the substance are acted upon by the 
protoplasm of the tissue, or by the protoplasm itself, by 
which there is ultimately formed carbon dioxide and water. 
The more active 1 these changes, the greater the heat pro- 
duced, and the larger the amount of carbon dioxide and 

iOne kilogram of coal yields the same quantity (same number) of calories, 
when oxidized slowly, as when oxidized rapidly ; but if two kilograms are con- 
sumed in one minute, they will produce twice the amount of heat for a unit of 



TISSUES PRODUCING HEAT. 327 

water formed. We should use the expression, " that the 
heat is produced by the metabolic changes of the tissue/ 7 
with caution; if by the statement we mean that the process 
consists in the tearing down of the protoplasm of the tissue, 
by the destruction of which the heat is produced, the state- 
ment is questionable. It is true that the protoplasm of the 
cell is the agency by which these oxidations are effected, but 
there is a question as to the protoplasm being the product 
from which the carbon dioxide and water are produced and 
the energy set free. There is no doubt that a very small part 
of the protoplasm of the cell may be used up in this process, 
but by far the greater part of the energy is produced by the 
oxidation of the substances furnished by the blood and 
lymph. 

The Tissues Producing Heat. — In any tissue in which de- 
structive metabolism takes place, heat is produced. The tis- 
sues differ greatly in their activity, and there will be a cor- 
responding difference in the heat they produce. The more 
important heat-producing tissues are, 

1. The Muscles. — The muscles, as we have learned, are 
very active tissues, giving off carbon dioxide during rest, as 
well as during muscular contraction. As they make up a 
large part of the body, and are very active tissues, they 
may be considered the chief source of the heat of the body. 
Even if we should disregard the heat produced by the quiet 
metabolism of the muscular tissues, it has been estimated 
that the heat produced by the muscular contractions would 
supply the principal part of the heat produced in the body. 

2. The Secreting Glands. — In the process of secretion, 
active metabolism takes place, and the heat thus produced 

time, and hence a greater temperature than if set free in two minutes, although 
in each case there will be the same quantity of heat produced. It Is the rate of 
oxidation that determines temperature. 

Clearly distinguish between quantity of heat and temperature. A pint of 
water may have a higher temperature than a hogshead of water, but it has a 
much less quantity of heat. Temperature is determined by the thermometer, 
and indicates the kinetic energy of the molecules, while quantity of heat means 
the total kinetic energy of the entire mass, and is determined by the product of 
the mass by the temperature. One gram of water at +100° C. has the same 
amount of heat as 50 grams of water at + 2° C, although the first is 98° 0. hotter. 



328 ANIMAL HEAT. 

will depend on their size, activity, and on the constancy of 
their action. As the liver is the largest and most active of 
the secreting glands, it produces the most heat. Its large 
size and constant activity place it next to the muscles as a 
source of the heat of the body. The blood on leaving the 
secreting glands is much warmer than it is on entering the 
glands. 

3. The Brain. — The cellular elements of the nerve tissue 
are engaged in active metabolic changes. We should expect, 
therefore, that the brain (the chief mass of cellular nerve 
substance), by its size and constant action, would give to 
the body considerable heat. That this is true is shown by 
the fact that the venous blood of the brain has a higher tem- 
perature than the arterial. 

The Loss of Heat. — There are various sources of the loss 
of heat ; the more important are — 

1. By Mechanical Work. — Of the energy set free by an 
organism, one fourth may be used up in mechanical work, 
and three fourths set free as heat. In estimating the amount 
of available energy in a given amount of proteid, fat, or 
carbohydrate, this must be taken into consideration, as the en- 
ergy used in mechanical work is lost as far as raising the 
temperature of the tissue and blood, and cannot therefore be 
a source of heat to the body. 

2. From the Surface of the Body. — This is by far the 
most important source of loss of heat, which takes place by 
radiation, conduction, and evaporation from the skin. This 
loss is due to the large surface presented by the skin for 
radiation and evaporation, and its large blood supply. Of 
this loss for every 100 calories of heat produced by the body, 
14.7 are lost by evaporation and 80.1 by radiation and 
conduction. 

3. From the Lungs. — When we consider the amount of 
surface 1 exposed by the mucous surface of the lungs, it would 



i The air cells of the lungs, if spread out side by side, would cover an area of 
2,600 square feet; if we add to this the surface exposed by the bronchial tubes 
and their numerous divisions, the surface exposed to loss of heat would be very 
much increased. To get the full surface exposed to loss we must add to that of 



QUANTITY OF HEAT. 329 

seem that this source of loss would be considerable ; yet, while 
next to the skin in importance, it is comparatively small. 
This is due largely to the fact that air inspired is heated 
by its passage through nasal fossae, pharynx, trachea, and 
bronchi, and is near the temperature of the blood before it 
reaches the lungs. If the depth and rate of the respiration 
be varied, the loss of heat will be somewhat modified. The 
loss by the lungs is 2.6 calories for every 100 produced. 

4. By ~W arming Cold Foods. — While this loss will vary 
with the temperature and quantity of the food, it is estimated 
to be 2.6 calories for every 100 of heat produced. 

If a large amount of cold liquids, as iced tea or water, 
be taken, the loss is very much increased. 

The Quantity of Heat. — The quantity of heat produced 
by the body will vary with the activity of the tissues and the 
quality and quantity of the food. In the resting adult it 
has been estimated at 2,400 calories per day or 100 calories 
per hour. In the resting adult of average weight this amount 
gives us thirty-four calories in twenty-four hours for each 
kilogram of body weight. By vigorous exercise this amount 
is increased to fifty-five calories for the same time. 

The heat-producing power of the foods varies even with 
a corresponding activity of the tissue. In complete 1 oxida- 
tion the heat values of the different classes of foods have 
been estimated to be as follows: 1 gram of proteid, 4.1 cal- 
ories; 1 gram of fat, 9.3 calories; 1 gram of carbohydrates, 
4.1 calories. The heat value of carbon is 8 calories; of 
hydrogen, 34 calories. 

the lungs the surface of the mucous membrane of the bronchi, trachea, larynx, 
pharynx, and nasal fossse. It is in the upper part of the course of the air pas- 
sages that most of the heat is lost. Taking in the entire air passages, It has 
been estimated that the loss here is fifteen per cent of the whole. 

i From what has been said, it might be inferred that the process of oxidation 
in the tissue is a simple one, and that the proteids break down at once into urea, 
carbon dioxide, and water, and the carbohydrates and fats into carbon dioxide 
and water. The oxidation of these substances is, in fact, very complex, and 
there are many transitions from the carbohydrate and the final products of its 
oxidation, carbon dioxide and water. The same is true of the oxidation of fat. 
Proteids are not completely oxidized in the body. Urea, the principal end prod- 
uct of proteid oxidation, is still capable of oxidation, and the estimate given 
above for the oxidation of proteids is the heat value of proteids less tha.t 
of urea. 



330 ANIMAL HEAT. 

Equalization and Control of the Heat The equalization 

of the heat is secured principally by the blood in its con- 
stant circulation from the more highly heated parts of the 
body to those of lower temperature, where the blood is cooled. 
On its return to the heated parts the blood tends to cool them, 
and by this constant exchange between the warm and the cool 
parts the heat is equalized. 

The control of the temperature of the body is due — 

1. To Regulation of the Production of Heat. — This is 
secured chiefly by the regulation of the metabolism of the cells 
which is effected by the nervous system. Some physiologists 
think there is a special heat center by which this is controlled ; 
others think the influence of the nervous system is only in- 
direct, in that it affects the blood supply through the vaso- 
motor nerves, and thus, by increasing the amount of blood 
in the tissue, increases or retards the metabolism of the tis- 
sue. Aside from the effect produced by the influence of the 
vasomotor nerves, there is both experimental and clinical 
evidence which indicates the existence of one or more heat 
centers similar to those which regulate the flow of the saliva 
and other secretions. These centers have not been located. 

2. By the Regulation of the Loss. — This is secured (a) 
by the use of proper clothing, which regulates the conduc- 
tion and radiation of body heat; (b) by the perspiration, 
which regulates the loss by evaporation; (c) the depth and 
rate of the respiration, deep respiration increasing the loss. 

Effects of Extreme Temperature. — The temperature of 
the body remains in normal conditions the same, notwith- 
standing the variable external temperature. The tempera- 
ture of a person in a torrid climate is within a degree Cen- 
tigrade of that of a person in a frigid climate. Persons 
have remained for some minutes in dry air in which the 
temperature was between 92° and 100° C, and persons have 
entered furnaces in which the temperature was 205° to 315° 
C. Such temperatures cannot be endured if the air is moist. 1 

i " C. James states that in the vapor baths of Nero, he was almost suffocated 
in a temperature of 44.5° C, while in the caves of Testaccio, in which the air is 
dry, he was hut little incommoded by a temperature of 80° C." — Kirk. 



HEAT REGULATION. 331 

These instances of adaptation to extreme temperature 
illustrate the perfection of the heat-regulating apparatus of 
the body. An increased loss of heat within certain limits 
produces an increased metabolism, and this in turn makes a 
demand for more food to furnish material to support the 
increased metabolism. The cold also causes the contraction 
of the blood vessels, which lessens the blood supply and the 
activity of the perspiratory glands, and thereby reduces the 
loss by conduction and evaporation. But there is a limit to 
this adaptation, so that the deficiency must be made up by 
clothing which further" reduces the loss, and by the increased 
metabolism by which the body maintains its equilibrium 
of temperature. If the external temperature be greater 
than that of the body, the decreased loss tends to lessen the 
metabolism. The higher external temperature also causes 
the blood vessels to dilate, increasing the blood supply, and 
thus exposing more blood to the surface of the body to lose 
heat by radiation and conduction; and at the same time, 
through the nervous mechanism of secretion and the in- 
creased blood supply, the activity of the perspiratory glands 
is increased, and thereby the loss of heat by evaporation 
increased. If, however, the atmosphere be humid, the air 
near the body soon becomes saturated with moisture, which 
checks the evaporation from the body, and thereby the loss 
of heat. The heat thus accumulates, and the body soon 
suffers from the intense heat. 

Normal Temperature of the Body. — From childhood to 
old age, through all seasons of the year, in arctic or torrid 
clime, at work or at rest, the body temperature remains 
practically constant, 1 varying one-half or one degree above 
or below 37° C. (98.6° F.). 

Fever may result from various causes, as specific germs, 

i Under morbid conditions the temperature of the body may rise above the 
normal. A rise above 37.2° C. (99° F.) indicates a feverish condition; 37.7° C. 
(100° F.) to 38.7° C. (102° F.), a moderate fever, 40° C. (104° F.) to 41.1° O. (105° F.), a 
high fever, and if the temperature of 41.6° C. (107° F.) or 422° C. (108° F.) is 
reached, and it be continued, death will soon result. 

The heated blood causes a great increase of the number of heart beats and 
respiratory movements until exhaustion is produced. 



332 ANIMAL HEAT. 

congestion, and inflammation. Bnt from whatever source, 
the increased temperature is mainly due to an increased heat 
production without a compensating loss of heat. 

The increase of the amount of carbon dioxide and urea 
excreted indicates an increased metabolism. This increased 
metabolism seems to produce a greater tissue waste than nor- 
mal metabolism, not only from the want of food, but also 
from the increased susceptibility of the protoplasm of the 
cells to change ; and the energy produced is set free as heat, 
and is not available as energy for mechanical work; hence 
the weakness and loss of flesh due to fever. 



CHAPTEB XIII. 
THE MUCO-DERMAL SYSTEM. 

EXPERIMENTS AND DEMONSTRATIONS. 

1. Examine a prepared section of the human skin, (a) 
with three-fourths objective. How many distinct layers do 
you notice ? Make a careful drawing. Compare with Eig. 
115, and determine names of parts, (b) Examine different 
portions of the slide with one-eighth or one-sixth objective. 
How many layers can you recognize ? Compare with Fig. 144. 

2. Make a vertical section of the eyelids of the cat. 
Harden by keeping in a twenty-five-per-cent solution of 
chromic acid for six or seven days; transfer to eighty- or 
ninety-per-cent alcohol, prepare a section as directed in Ap- 
pendix. Examine as directed in Experiment 1. 

3. Make a vertical section of the skin of a rat, and pre- 
pare as given in Experiment 2. Examine as directed in 
Experiment 1. Study and determine name of parts observed. 

4. Treat a fresh hair with concentrated acetic acid, which 
will bring to view the cuticle and the parts of the medulla. 
(a) Examine with low and high power objectives. (&) 
Treat some fresh hair with sulphuric acid by heating in the 
acid at a temperature 40°- 50° C. for an hour. This will 
isolate the plates of the cuticle and the fiber cells of the sub- 
stance of the hair. Examine as before, (c) The elements 
of medulla may be very clearly seen by soaking the hairs 
in a two-per-cent solution of caustic potash for several days. 
Make drawings of what you observe, (d) Examine hair of 
different animals, and compare. 

5. Take a piece of the skin from the ball of the foot of a 
cat, harden in chromic acid and alcohol. Note (a) the ter- 
minal gland coil in the outer part of the subcutaneous tissue. 
Are they all located at the same level? (b) the gland duct. 
Determine parts by comparing with Eig. 144. 

6. Examine the palm of the hand with a reading glass 
or a Coddington magnifier of threc-fourths-inch focus. No- 
tice the number and arrangement of the pores. 

333 



334 MUCO-DERMAL SYSTEM. 

7. When perspiring freely, notice the condition of the 
blood vessels. What reason can yon give for this condition ? 
Collect a few drops of the perspiration. Test first with blue 
litmus paper, then with red litmus. What is its reaction? 
Examine a drop of perspiration with the microscope. 

8. Dip a platinum wire (No. 30) ending in a small loop 
and about two inches long in some perspiration, and then 
hold the loop in the nonluminous flame of a Bunsen burner 
or candle. If it colors the flame yellow, it indicates the 
presence of sodium in the perspiration. Look at the flame 
with a blue glass; if the flame appears purple, it indicates 
potassium. To fifteen or twenty cubic centimeters of per- 
spiration add a few drops of a solution of silver nitrate. If 
you get a white precipitate, it indicates the presence of a 
chloride. This in connection with a yellow flame shows the 
presence of sodium chloride. 

9. To 10 c.c. of perspiration add 5 c.c. of baryta water, 
filter, and to the filtrate add, drop by drop, a solution of 
nitrate of mercury until the precipitate gives a yellow reac- 
tion with sodium carbonate, which indicates the presence 
of urea. 

10. To 5 or 10 c.c. of perspiration add a few drops of 
barium chloride; the formation of a white precipitate indi- 
cates the presence of sulphates. 

11. To 15 or 20 c.c. of perspiration add 5 or 10 c.c. of 
lime water ; if the solution becomes turbid, or there is formed 
a white precipitate, it indicates the presence of carbon diox- 
ide. Write a summary of what you have learned in these 
experiments about the composition of perspiration. 

12. Place the hand in a clean quart glass fruit jar or 
bell- jar; cover the mouth of the jar, and the portion of 
the hand outside of the jar, with sheet rubber so as to exclude 
the air from the jar. Keep the hand in the jar as long as 
you can. Keep the jar moderately cool. 

What is the source of the moisture that collects on the 
side of the jar? What do you learn from the experiment? 

13. Place the hand for a few minutes in warm water 
38° C, then for the same length of time in cold water 4° C. 
How do you account for the different appearance of the skin 
in each case ? 

14. (Problem.) If the total number of sweat glands is 
2,500,000, and their average length is one fourth of an inch, 



EXPERIMENTS. 335 

how long a tube would they make if put end to end ? Give 
your answer in miles. What would be their total caliber if 
they were placed side by side, if the pores by which they 
open is one six-hundredth of an inch in diameter ? Give 
your answer in square feet. 

15. Put a few drops of ether in the hand, and notice the 
sensation produced by its evaporation. How do you account 
for the cool sensation ? 

16. When the water in the teakettle is boiling, remove 
the kettle from the stove and place your hand on the bottom 
of the kettle. Why does it not burn the hand ? What effect 
would the evaporation of the perspiration have upon the tem- 
perature of the skin? 

17. Examine the teeth of an adult. How many are 
there ? How do they differ in size and form ? As to their 
form, into what four classes can they be grouped ? How 
many teeth are there in each group ? Determine from the 
text names of the four classes of teeth. What reason can you 
give for the difference in the shape of the teeth ? Do you 
see any reason for the teeth of an ox being different from 
those of a dog ? 

18. Examine the teeth of a child six or seven years old. 
What difference do you note in the number and form of his 
teeth ? Into what classes can they be grouped ? What name 
is given to the teeth of the child ? Why do children shed 
their teeth ? What name is given to the teeth of the adult ? 

19. Secure from the dentist some teeth, and compare the 
structure of the milk teeth with those of the permanent teeth. 
Compare the form and size of the incisors, canine, bicuspids, 
and molars, and note how they are adapted to their respec- 
tive function. 

20. Examine, and by a study of Eig. 147 determine the 
parts of a tooth. 

21. Examine longitudinal and cross sections of teeth, 
and determine their structure. How do the different parts 
differ in hardness? Will the upper hard part of the tooth 
scratch glass ? Why is it so hard ? Make thin vertical and 
cross sections of a tooth, and examine with the microscope. 

22. Examine the skeleton, and determine how the teeth 
are set in the jaws. How do the nerves and blood vessels 
go to the teeth ? What is the purpose of the hole in the fang 
of the tooth ? of the cavity of the tooth ? 



336 MUCO-DERMAL SYSTEM. 

23. Determine the composition of the teeth in the same 
manner as yon did for that of the bone. Which has the 
more water? Which the more carbonates? Test the teeth 
for silicates (see Appendix). 

THE MUCO-DERMAL SYSTEM. TEXT. 

The Skin. — The covering of the body is called the skin 
(Fig. 142). At the orifices of the body, as the mouth and 
nostrils, and some other parts, it becomes gradually blended 
with the mucous membrane that lines the interior of the 
body. As we have seen, the skin and the mucous membrane 
are very much alike, each being made up of an outer cell 
layer resting upon an inner fibrous layer. Each has its own 
modification, however, to adapt it to its peculiar function. 

The thickness of the skin varies in different parts of the 
body; where exposed to pressure and friction, as on the soles 
of the feet, and in the palms of the hands, it is much thick- 
ened. The skin is elastic, and tends to adapt itself to the 
change of form in the organ it invests. When viewed under 
low power, the skin is seen to be composed of two layers : an 
outer, cellular layer, the epidermis; and inner, fibrous layer, 
the derma. 

The Epidermis, or Cuticle. — The epidermis (Fig. 12) 
consists of (1) the superficial horny layer of flattened cells; 
(2) a layer formed of dense, horny scales showing traces of a 
nucleus, the stratum lucidum; (3) a layer consisting of sev- 
eral layers of nucleated cells, the deeper ones of which become 
columnar as they rest on the underlying corium or dermis, 
the rete mucosum. It is in the deepest parts of the cell layers 
of the epidermis that the new cells are formed by cell divi- 
sion. The cells are pushed outward from below, and as they 
near the surface, they not only become compressed and 
changed in shape, but they undergo a change in chemical 
composition, their protoplasm being converted into a horny 
substance (keratin). Before their transformation into the 
horny layer, there is usually a deposit of granular material 
within the cells, which gives a granular appearance to the 
upper layers of the rete mucosum. The color of dark-col- 



COMPOSITION OF THE SKIN. 



337 



ored races is due to pigment granules contained chiefly in the 
cells of the deeper layer of the rete mucosum. The older 
cells are constantly being removed by wasting and friction, 
and constantly renewed from below. 

The Dermis, or Corium. — This layer is also called the 
true skin (Fig. 1-i-i), or cutis vera. It varies in thickness in 
different parts of the body, being from one twelfth to one 
eighth inch in some cases, in others only one hundredth, as 




, Fig. 142.— Vertical. Section of the Skin. 

1. Outer horny layer. 2. Stratum lucidum. 3. Eete mucosum. 4. Papilla. 
5. The corium (derma). 6. Duct of sweat gland. 7. Sweat glaud. 8. Artery, 
y. Subcutaneous fat. 

in the lips and ear passages. It is made up of an interlacing 
network of white, fibrous connective tissue, with some elastic 
fibers, numerous blood vessels, lymphatics, and nerves; and 
gradually becomes blended below with the subcutaneous 
tissue, through a layer of areolar tissue of varying thickness 
containing fat cells. On its upper surface are numerous 
small projections (papilla?) which protrude up into the epi- 
dermis, the innermost layers of the epidermis being molded 
over the papillae, and forming processes between them. The 
papillae are very sensitive, and consist of vascular eminences, 
conical or club-shaped, about one hundredth of an inch in 
height, which contain capillary loops; most of them have 
22 



338 MUCO-DERMAL SYSTEM. 

also one or more nerve fibers, those of the hands and feet 
ending in a touch corpuscle. Fine nerve fibers also pass 
into the epidermis, where they end between the cells or in 
the deep epithelium. 

On the general surface of the body the papillae are com- 
paratively few in number, but in sensitive parts, as the palm 
of the hand and fingers, they are numerous. On the palm 
of the hand they are arranged in parallel curved lines, form- 
ing the elevated ridges seen on the free surface of the skin. 

The Sweat Glands. — The sweat glands, called also su- 
doriferous glands, are found in the human skin in nearly all 
parts of the body, their total number being over 2,500,000. 
They are most numerous in the palms of the hands and the 
soles of the feet, and largest in the axilla? and groin. They 
are comparatively few in the neck and back. The pores, or 
openings, of the ducts are about one six-hundredth of an inch 
in diameter, and are visible with a lens of moderate power. 
Each gland consists of a single tube with a closed end, form- 
ing a closed coil about one sixtieth of an inch in diameter, sit- 
uated in the deep part of the dermis or in the subcutaneous 
fatty tissue. This is the secreting portion of the gland, and 
is surrounded by a network of blood vessels. From the coil 
the duct passes upward in a somewhat wavy course through 
the dermis, but takes a spiral direction on entering the epi- 
dermis upon whose surface it empties. 

The secreting portion consists of a fine basement mem- 
brane, a layer of longitudinally disposed fibers, which are 
usually considered muscular, and a single layer of columnar 
epithelium lining the central cavity. 

The conducting tube, which includes about one fourth of 
the coiled part, has a basement membrane of epithelium of 
two or three cell layers, an internal delicate lining, and the 
tube, or lumen. It has no muscular layer, and the tube is 
smaller than the secreting portion. In its passage through 
the epidermis, it is only a channel through the epithelial cells. 

The Sweat, or Perspiration. — The secretion of the per- 
spiratory glands is called sweat, or perspiration. It consists 



THE PERSPIRATION. 339 

of 98.8 per cent water, 1.2 per cent of solids in solution, a 
few shed scales of the epidermis, and a small amount of 
sebaceous material. The chief solid products are sodium 
chloride, fats, and fatty acids, and traces of urea. When 
scanty, its reaction is acid; but when abundant, alkaline. 
The amount of carbon dioxide given off by the skin is very 
small, being only ten grains in twenty-four hours, while a 
corresponding amount of oxygen is absorbed. Cutaneous 
respiration in man and other mammals is, therefore, very 
slight. Eabbits or other mammals covered with gold foil 
or coated with varnish to prevent the escape of the perspira- 
tion, do not die from the effect of the carbon dioxide not 
being excreted, as was formerly supposed, but rather from 
excessive loss of heat by too rapid radiation. 

If wrapped in cotton, the animal will live for some time. 
In such animals as the frog, which have a thin skin, the 
cutaneous respiration is of much importance. 

When the secretion of the perspiration is small, it passes 
off as rapidly as formed, and is called insensible perspiration. 
If the amount is large, or if it forms in drops due to its form- 
ing more rapidly than it evaporates, it is called sensible per- 
spiration. The amount of sensible perspiration is influenced 
by the humidity of the atmosphere, the temperature, and the 
muscular exercise. The total amount of perspiration se- 
creted in twenty-four hours by a man is nearly 1,000 grams, 
or over 2.2 pounds. 

The blood vessels have the power of changing their cal- 
iber : by dilating, they bring to the part more blood ; by con- 
tracting, they reduce the amount of blood. As we shall learn, 
this power to change the size is under the control of the nerv- 
ous system. An increase of blood supply tends to increase the 
activity of the secretions in the sweat glands. In addition 
to this source of increasing the amount of perspiration, there 
are parts of the spinal cord, the direct stimulation of which 
produces an increased flow of the perspiration. These parts 
are known as sweat centers. There are drugs and agents 
which affect these centers which the physicians give when 



340 



MUCO-DERMAL SYSTEM. 



they want to produce sweating. These drugs and agents are 
called diaphoretics, as hot baths (98°-100° 
F. ), hot teas, alcohol, pilocarpine, and 
sweet spirits of niter. 

The sweat glands act as excreting 
organs. They remove from the system, 
water, mineral salts (principally sodium 
chloride), fats, acids, and some urea and 
carbon dioxide. 

There is a close relation between the 
activity of the kidneys and the skin. When 
the skin becomes inactive, it throws more 
work on the kidneys, and conversely inac- 
tive kidneys make a greater demand on the 
skin. 

The perspiration aids in regulating the 
temperature by its evaporation. How this 
is done you may learn by Experiment 15. 
Functions of the Skin. — The more im- 
portant functions of the skin are, (1) to 
protect the delicate parts of the body; (2) 
to prevent too rapid radiation of the heat 
of the body, which would take place were 
it not for the skin being a poor conductor 
of heat; (3) to regulate the temperature 
of the body by means of the perspiration, 
also by controlling the amount of blood ex- 
posed to loss of heat by means of the con- 
traction or dilation of the cutaneous blood- 
vessels ; (4) to act as an organ of absorp- 
tion, as water and a number of substances 
may be taken up by the skin; (5) to remove waste materials 
from the body by means of its excretions; (6) to sever as 
an organ of the sense-touch, some of the papillae of the skin 
containing the end organs of the nerves of touch; (7) to 
secrete the perspiration and the sebaceous material for the 
protection of the skin and hair. 



Fig. 143.— Hair and 
Hair Follicle and 

Sebaceous Gland. 

1. Outer sheath. 2. 
Inner sheath. 3. Hair 
follicle. 4. Hair. 5. 
Papilla. 6. Sebaceous 
gland. 



HAIR AND NAILS. 



341 



mi 



: 



Hair and Nails. — These organs are modifications of the 
epidermis. The hair is developed in pits which often extend 
down into the dermis. The parts of the 
hair (Fig. 1-13) are the root, the part 
found within the follicle, and the shaft, 
or the free portion. The root consists 
of soft growing cells fitting over a vas- 
cular papilla. The shaft is made up of 
a central pith, or medulla (Fig. 144), 
formed of angular cells. This layer is 
sometimes absent The fibrous part 
consists of long, tapering cells united to 
form fusiform fibers. This layer forms 
the chief part of the hair. The outer 
layer is called the cortex, or cuticle. It 
consists of thin, flat cells overlapping 
each other. 

The pit, or follicle, is formed by 
two coats ; an outer, or dermic, continu- 
ous with the corium of the skin ; and an 
inner, or epithelial, called the root 
sheath. The hair grows from the bot- 
tom of the follicle by the multiplication 
and elongation of cells covering the 
papilla. Connected with the papilla 
are small bundles of muscular fibers 
(erectores pili), which pass from the 
corium to the bottom of the follicle. By 
their contraction they not only erect the 
hair, but also raise one part of the sur- 
face of the skin, and depress another. 

Sebaceous Glands. -The sebaceous 
glands are simple sac-shaped glands 
found all over the surface of the body, 
except in the palm of the hand and 
soles of the feet. The duct usually opens into a hair follicle 
(Fig. 143), though some, in a few situations, open free on 



.( 






Fig. 144.- Vertical Sec- 
tion of Hair Follicle 
with Hair. 
4 and 5. Medulla. 6. 
Inner root sheath. 7. 
Outer root sheath. 8. 
Bulb. 9. Papilla. 10. 
Root. 



342 



MUCO-DERMAL SYSTEM. 



the surface of the skin. Both the duct and the sac of the 
gland are lined with secreting cells, some of which become 
charged with fatty matter. Excretion appears to take place 
by the rupture or disintegration of the loaded cells, the trans- 
formed cells and their contents being pushed out of the duct 
through the hair follicle on the surface of the skin by the 
new cells from behind. The excretion 1 (or probably more 
properly the secretion) appears when fresh to be an oily sub- 
stance that sets, on cooling. It is made up of fatty particles, 
crystals or organic substances, and epithelial cells. 

The Nails are implanted in a groove in the skin by a 
portion called the root, and grow from a portion of the true 
skin called the bed, or matrix. The nail consists (Fig. 145, 
A and B) of horny cells having a laminated structure, the 
deepest layers lying in contact with the papillae of the matrix. 
The nail grows by the formation of new cells at its root, and 
on the under surface. 

The Teeth. — When functionally considered, the teeth 
should be classed with 

liili 



the digestive apparatus ; 
but when considered as 



4__ 





Fig. 145.— The Finger Nail. 
Vertical Section of Finger. 
1. Body of nail. 2. Wall or 
covering of root of nail. 3. Sec- 
tion of last phalanx. 4. Matrix. 



Fig. 146.— Magnified Section Through 

Nail. 
1. Outer horny layer. 2. Cellular layer. 

3. Outer layer of the cuticle layer of the nail. 

4. Cuticle. 



to their origin and structure, they belong to the same system 
of organs as the skin and mucous membrane, and are to be 
considered as modified epithelial growths. 

The teeth are located in the alveolar processes of the in- 



iThe sebaceous secretion contains lanolin (a fat of cholesterin), which, by 
not becoming rancid, protects the hair and skin. 




£ — ? r. ~i « ~ ST 

|3§ M li* Q9 



_ ~-2~~z ~ — ~ 



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" > C 3 -• e» S — : T. - 

c v- r * £ — i — ~ • 



5 « g r C 



3U p 



= co l 



I D EL^H < - s 




THE TEETH. 



343 



ferior and superior maxillary bones and in the gums, which 
are a modification of the mucous membrane. 

Parts of a Tooth. — A tooth (Fig. 147) consists of the 
part projecting from the gums, called the crown; of a con- 
stricted portion, the neck, and the part occupying the alve- 
olus, called the fang, or root. 

Varieties of Teeth. — The teeth (Fig. 95) are of four 
varieties : the incisors, or cutting teeth, the canines, bicuspids, 
and molars, or grinders. 

The incisors have the crown wedge 
shaped, convex in form, beveled and 
slightly concave behind; the fang is 
single, long, and conical. The canines 
have conical crowns and conical fangs. 
They rise above the level of the other 
teeth. The upper pair are commonly 
known as the "eye teeth," and the lower 
as the " stomach teeth." The cuspids 
have two cusps projecting from the 
crown and a single fang; they are also 
called premolars. The molars have a 
nearly cubical form, with four cusps on 
the upper molars and five cusps on the 
lower molars. The first two upper mo- 
lars usually have three fangs, while the 
first two lower have two fangs. The 
third molar is called the " wisdom 
tooth," on account of its appearing so late. It usually has 
but one fang, but shows a tendency to form other fangs. 

Structure of a Tooth — The body of the tooth is com- 
posed of a substance called dentine, or ivory, which consists 
of wavy branching tubes, called dental tubes, imbedded in 
a hard intertubular substance; the tubes are about ^Vf ^ 
an inch in diameter. Dentine is composed of twenty-eight 
parts of animal matter and seventy-two of mineral matter. 
The thin crust on the crown is called enamel. It is the 
densest tissue of the body, has but 3.5 per cent of animal 




Fig. 147.— Vertical, Sec- 
tion of a Tooth. 
land 2. Crown of tooth. 
The construction por- 
tion, the neck. The low- 
er projections, the roots 
or fangs. 1. The enamel. 
2. The dentine. The 
outer covering of the 
roots, the cementum. 3. 
Tooth cavity and pulp. 



344 MUCO-DERMAL SYSTEM. 

matter, and is made up of hexagonal rods (enamel columns), 
which are about -5V0 o of an inch in diameter. 

The fang of the tooth has an outer layer of true bone, 
which covers the fang from the neck down, and is thicker at 
the apex of the fang. This layer is called the cementum, or 
crust a petrosa. 

The cavity of the tooth is filled with the tooth pulp, which 
consists of a soft, very vascular connective tissue, with numer- 
ous nerves and cells, the latter being of two kinds : the colum- 
nar, or odontoblasts, arranged in a layer lining the pulp cav- 
ity, and the stellate and fusiform, which permeate the pulp 
substance. 

Dentition. — By dentition 1 is meant the time and man- 
ner of appearing of the teeth. With milk teeth this is a 
very critical time with the child, the appearance (cutting) 
of a tooth producing a great disturbance of the health of the 
child. The dentition of the permanent teeth produces very 
little disturbance except that of the " wisdom tooth," which 
is sometimes very painful, and interferes with the general 
health. 

Nerves of the Teeth The nerves and blood vessels of 

the teeth enter the jaw at an opening called the dental for- 
amen, and enter the teeth by means of openings in the fangs. 

Care of the Teeth. — The teeth, properly cared for, will 
last a long time. If, however, they are subjected to extremes 
of hot and cold liquids and other substances, the enamel soon 
becomes broken, making the teeth easy of decay. Particles of 
food left between the teeth after eating should be removed, 
and the teeth thoroughly washed with a toothbrush. If the 
food is not removed, it tends to produce, by decomposition, 
acids and products which are not only injurious to the teeth, 
but to the general health as well. 

i The arrangement and number of the teeth are represented by a diagram 
which shows half of the jaw with initial letter of the teeth; such a formula is 

called a dental formula. For the milk teeth it is igZci — M 2 making ' forthe 

t (> /~i i g o ]y[ 3 

whole number, twenty. For the permanent teeth, £ g _ q* 1 _ B 3 _ m 3 makiDg ' for 

t-he whole number, thirty-two, 



BATHING. 345 

The Necessity for Bathing. — The skin is one of the chief 
channels for the excretion of waste products. The perspira- 
tion contains fatty substances, organic and mineral salts, 
dead epithelial cells, and water. When the liquid portion 
of the perspiration evaporates, it leaves the solid substances 
on the surface of the skin, and with these may collect dust 
and dirt, and sometimes germs of disease. This layer of im- 
purity may in several ways be injurious to health. 1. It 
tends to clog the pores of the skin, thus preventing the perspi- 
ration, and checking the proper action of the skin, one of 
the principal organs of excretion. The skin failing to do 
its duty, additional work is thrown upon other organs, chiefly 
the kidneys and lungs. This extra work will in time ex- 
haust the overtaxed organs, and bring about serious diseases. 
2. This layer of material on the surface forms a favorable 
condition for the development of bacteria, and many skin 
diseases may result from such neglect. 3. This unwholesome 
layer favors parasitic skin diseases. 4. When the skin can- 
not perform its proper function, the individual is more 
liable to take cold. We should be as careful about the clean- 
liness of our person as we are about the food we eat or the 
clothes we wear. 

Aside from cleanliness, bathing has a marked effect upon 
the general system, which will vary with the kind of bath. 
Its general effects are as follows : a. The cold bath, which may 
range in temperature from 0° C. to 15 °C. Its effects are to 
cool the blood in the cutaneous vessels; stimulate the heart 
and respiration; raise the blood pressure by temporarily 
overfilling the internal blood vessels. It is useful as a refrig- 
erant in fever ; refreshing to the strong and to those in good 
health ; may be used as the morning bath. b. The cool bath, 
which has a temperature from 15° C. to 22° C, has a similar 
effect to the cold bath, but less marked. It may be used by 
persons weaker than those who take the cold bath. c. The 
tepid bath ranges in temperature from 20° C. to 34° C, 
acts both chemically and physically as a cleansing agent; 
soothes the nerves. Its chief uses are for ordinary personal 



346 MUCO-DERMAL SYSTEM. 

cleanliness; to allay the restlessness of fever, and to lower 
temperature, and as a sedative when one is nervous and ex- 
hausted by overwork. This may be used as the evening bath, 
and by the most delicate, d. The warm bath should have a 
temperature of 34° C. to 38° C. Its general action is to raise 
local temperature and circulation, stimulate glands, soothe 
the nerves to the corresponding centers, produce perspiration 
in fevers, and act as an anodyne and antispasmodic. This 
bath may be used by any one. e. The hot bath has a tem- 
perature from 38° 0. to 41° C. Its effects are similar to 
those of the warm bath, but more powerful. When applied 
locally, it attracts the blood to the part bathed and from dis- 
tant parts. We have seen in the study of circulation why it 
is used to relieve internal congestion, as in colds, etc. 

The benefit of the bath depends much upon the time and 
manner in which it is taken. The bath should not be taken 
just before, nor immediately after, a meal. The cold bath 
should not be used when the body is greatly exhausted by 
severe mental or muscular exercise. A bath is more beneficial 
in the forenoon than in the afternoon. 

Cold baths should not be taken when the person is chilly, 
perspiring, or by persons in a weak condition. The bath 
should be taken briskly, the skin well rubbed and quickly 
dried. Exercise should follow most baths. If the mind is 
brighter, and the skin has a healthy glow, and exhilaration 
follows, the bath has been beneficial ; but if languor follows, 
the skin is blue to pale, and there is a sensation of chilliness, 
then it has been injurious, and reaction should at once be 
brought about by vigorous rubbing or by exercise. 

Hot baths have a relaxing influence on persons of weak 
hearts or suffering debility, and they may faint while taking 
them. Persons suffering from heart disease or chronic dis- 
ease of any important organ should not take frequent cold 
baths. 

Outdoor bathing should not be taken for an hour or two 
after a full meal, nor just before a meal, especially before 
breakfast. 



CARE OP THE HAIR AND NAILS. 347 

Salt water is more stimulating to the skin than fresh 
water. To those in health it is refreshing and invigorating, 
but the bather should come out of the water as soon as there 
is the slightest feeling of chilliness. Too frequent bathing 
may prove more injurious than beneficial. It should not be 
engaged in more than once a day, except by the very vig- 
orous. 

Care of the Hair and Nails. — The hair should be fre- 
quently washed, but the use of much soap may prove injurious 
by destroying the natural secretion of the oil of the hair, 
making the scalp dry and hard. The hair should be brushed 
with care, as brushing it too long or too hard may stimulate 
the scalp, causing an increase of the scurf. A similar result 
may be produced by using too stiff a brush. Hair dyes and 
hair oils should not be used, as in most cases they contain 
substances which are not only injurious to the hair but also 
to the health. 

The nails should be kept of proper length. When not 
kept clean, they become not only unsightly, but may serve 
as carriers of disease germs. Sores and wounds should never 
be picked with the nails. If they are permitted to grow too 
long, they are liable to be broken off, which not only injures 
their appearance, but their texture as well. 

They should be kept of the proper length by filing, rather 
than by cutting, and never by biting them off. In removing 
dirt from beneath the nails, hard instruments should never 
be used, but a toothpick or an ivory cleaner. In no case 
should the nails be trimmed to the quick, or their surfaces 
scraped. The latter tends to make the nails thick and rough. 
They should be cleansed with a nail brush, which will not 
injure the smooth and polished surface. 

How Alcohol Affects the Skin.— When strong alcohol is 
applied to the epidermis, it tends to harden it. Bathing 
the skin with alcohol in case of protracted disease prevents 
bed sores by hardening the outer surface of the epidermis. 
It tends also to stimulate the skin; this is seen by the red- 
ness of the skin when bathed in strong alcohol. Taken 



348 MUCO-DERMAL SYSTEM. 

internally, it has marked effect on the skin, congesting its 
blood vessels. This condition, if the drinking becomes habit- 
ual, becomes chronic, and may bring about a disordered con- 
dition of the skin and modification of the activity of the 
glands. The soft, satiny feeling in the skin is one of the first 
evidences that the person is drinking to excess, and a warning 
of the more serious evils to follow. 

Later on, the skin becomes thick and discolored, some- 
times red, and in some cases sallow; in this condition it 
becomes liable to various diseases. At first the cheek and 
nose have a healthy glow of red, but later on they become 
more congested, and a purple takes the place of the red, 
showing by the increased size of the vessels a chronic con- 
gestion of the blood vessels, as well as a diseased condition 
of the blood. 



CHAPTER XIV. 

THE KIDNEYS. 
EXPERIMENTS AXD DEMONSTRATIONS. 

1. Get from the butcher the kidneys and bladder of the 
hog or sheep (do not cut the kidney loose from the connec- 
tion with the bladder). Xotice, 

a. Relation of Kidneys to the Bladder. — Where do the 
tubes (ureters) from the kidneys to the bladder enter it? 
Do you see any advantage in this arrangement? 

b. The Position of the Fat. — Do you see any reason 
for this large amount of fat ? 

c. The Cap-shaped Body (Suprarenal Capsule) Covering 
the Upper Part of the Kidney. — Does it have any duct? 
Has it any connection with the kidney? Make several sec- 
tions of the capsule, put them into sixty-per-cent alcohol, and 
make permanent mountings, as directed in the Appendix. 

d. The Form, Size, and General Appearance of the Kid- 
neys. — How do the blood vessels enter the kidney? 

e. The Large Artery (Renal) Entering the Kidney. — 
Prepare an injective mass as directed for the veins under 
subject of circulation, but in place of the chrome yellow 
use carmine, which should be added while the gelatin is hot 
and thoroughly stirred to secure complete mixing. Tie the 
free portion of the renal artery securely to a canula of con- 
venient size, and inject the arteries as directed under cir- 
culation. 

/. The Large Vein Entering the Kidney. — Prepare an 
injection as directed in e, but use in place of carmine, chrome 
yellow (see Circulation). Inject the veins with this mass. 

Cut the injected kidney loose from the ureter, one or two 
inches from where it enters the bladder. When the injection 
mass is well set, make a section of the kidney so as to divide 
it into halves flat-wise (Pig. 148), and then determine the 
structure of the kidney. Examine the different portions of 
one of the halves of the injected kidney with the dissection 
microscope. Make thin sections of the cortical and medul- 

349 



350 THE KIDNEYS.. 

lary portions; mount in glycerin, and examine with a two- 
thirds or three-fourths objective. 

2. Make permanent mounts of different parts of the unin- 
fected kidney, especially of the cortical portion, the medul- 
lary portion, a pyramid, the mucous membrane of the pelvis. 
Examine with two-thirds and one-fourth objectives. 

3. Prepare a permanent mount of longitudinal and cross- 
section of the ureter. Examine under high and low power 
objectives. 

4. Tie the free end of the portion of the ureters connected 
with the bladder, and inflate the bladder by blowing through 
a glass tube securely fastened in the large exit tube (urethra) 
of the bladder ; and when inflated, tie the urethra so that the 
bladder will remain inflated. Compare the capacity of the 
bladder with the total capacity of kidneys. What does this 
indicate in regard to the constancy of the secretion of the 
urine? What evidence do you see of muscular tissue? of 
elastic tissue? of inelastic tissue? 

5. Examine the entrance of the ureters into the bladder. 
Is there any means to prevent the reflow of the urine back 
into the ureters when the urine is being expelled from the 
bladder ? 

6. Verify your conclusion made in regard to the struc- 
ture of the bladder by examining both teased specimens and 
sections of the bladder. 

1. Examine longitudinal and cross-sections of the 
urethra. 

Compare your observation with the statements given in 
the text. 

THE KIDNEYS. TEXT. 

As has been stated, the three most important waste prod- 
ucts of the body resulting from its complex metabolism are 
carbon dioxide, urea, and water. 

The lungs provide for the elimination of the greater part 
of the carbon dioxide and of some of the water ; the skin, for 
some of the water, a small per cent of the carbon dioxide, and 
a small amount of urea. The principal waste product re- 
sulting from the nitrogen metabolism is urea. Eor its excre- 
tion there is provided a special apparatus consisting of the 
kidneys, the ureter, bladder, and urethra. 



STRUCTURE OF THE KIDNEYS. 



351 



Where and how urea is formed we are still in donbt. 
There are many reasons for believing that it is not secreted 
by the kidneys, as was formerly supposed. If we are to 
believe recent experiments and investigation, the liver is the 
chief o r g a n 
concerned 
with the secre- 
tion o f urea, 
and the kid- 
neys with its 
excretion or 
elimination. 

Structure of 
the Kidneys. 
— The two 
kidneys are 
situated in the 
posterior part 
of the abdom- 
inal cavity, be- 
hind the peri- 
toneum and 
intestine, close 
to the spinal 
column, one 
being on each 
side, on a level 
with what is 
called the 
waist, or loins 
(Fig. 6). The 

kidneys are surrounded by a mass of fat and loose areolar 
tissue, having its upper portion capped by a body called the 
suprarenal capsule. They are of a dark brown color, of char- 
acteristic shape, resembling that of the lima bean, but much 
thicker in proportion. Their weight varies from four to six 
ounces. 




Fig. 148. — Longitudinal Section of the Kidney. 
1'. Medullary rays. 1". Labyrinth. 1. Cortex. 2. Medulla. 
2* . Papillary portion of medulla. 2". Boundary layer of 
medulla. 3. Tranverse section of tubules in boundary 
layer. 4. Fat of renal sinus. * Tranversely crossing med- 
ullary rays. 5. Artery. 6. Renal artery entering at hilum. 
7 Renal calyx. 8. Ureter. 15. Pyramid. 16. Pelvis. 



352 THE KIDNEYS. 

They are covered by a dense, tough fibrous capsule, being 
connected to the substance of the kidney by fine processes 
of connective tissue and minute blood vessels, from which it 
can be easily removed. Their internal surface is concaved, 
forming a deep longitudinal fissure, the Mlum allowing the 
passage of the blood vessels, nerves, and ureter into and 
out of the organ. 

A vertical section of the kidney presents for study the 
outer deep red portion, the cortical, and the inner pale red 
portion, the medullary, or pyramidal portion, entering into 
the composition of which are twelve papillae, or pyramids, 
whose apices project into a funnel-shaped cavity called the 
pelvis, formed by the dilation of the excretory duct, the 
ureter, which is divided into several truncated branches or 
infundibula, called calices, around the apices of the pyra- 
mids. The cortical substance also invests the bases of the 
pyramids, sending off between them what are known as the 
columns of Bertin. In texture the Cortical substance is soft 
and friable, and under lower power shows small granules, 
due to the Malpighian corpuscles. 

The medullary portion consists of two layers, the outer, 
or boundary, layer, and the papillary part, denser than the 
cortex, and presenting strise, or radial streaks, passing into 
the cortex, and there called medullary rays, or pyramids of 
Ferrein. The portion of the cortex lying between the medul- 
lary rays is called the labyrinth, in which is found the gran- 
ular bodies, the Malpighian bodies. By examining the apices 
of the pyramids with a low-power lens, small openings will 
be found, through which the urine exudes into the calices 
of the pelvis of the kidneys. 

Microscopic Structure.— On microscopic examination the 
kidney is found to be very complex in structure. It is made 
up of blood vessels, tubules, bound together by a small amount 
of connective tissue. The kidney is, in fact, a compound 
tubular gland, the unit of which is the tubuli uriniferi (Fig. 
149, B), or tubes which carry the urine. They arise in the 
cortex by a cup-shaped expansion, the Malpighian capsule, 



STRUCTURE OF THE KIDNEYS 



353 



afterward pursuing a complicated course, and uniting with 
other tubes to form collecting tubes which discharge their 
contents into the calices by small 
openings at the end of the pyr- 
amids. The uriniferous tubules 
are found in both cortex and 
medullary portions, being for the 
most part contorted tubes in thf> 
cortex, and straight tubes in the 
medullary portion. The Mal- 




4 
Fig. 149. B. — Malpighian Body. 
Vessels coming to glomerule (vas affer- 




ens) and vessels going from glomerule (vas 
efferens). 2- Glomerule. 3. Oapsule of glom- 
erule. 4. Contorted tubule. 

pighian body from which the 
tubules arise are about one one- 

hundred-and-twentieth inch in FlG . 149 . A . -diagram of Struc- 
diameter, each capsule inclosing L Malp ™ an ° bod^Trirst con- 
a bunch of convoluted blood cap- r^&^^JoSSiVfffr 
illaries called a glomerulus (Fig. ^i^^iSSS'g tuSS^ai? 
149 B). The tubule consists of Jff c t w ?Su^Sf SffiSi 2-pSS?SS 
a layer of epithelial cells resting apexof the w» u ^- 
on a basement membrane, the blood vessels being brought 
into close connection by an arrangement soon to be described. 
23 



354 THE KIDNEYS. 

The tubule leaves the capsule by a narrow neck, which 
soon becomes twisted on itself to form the first convoluted 
tubule, which straightens somewhat to form the spiral tubule, 
then passing straight downward becomes smaller, and passes 
into the medullary portion to form the descending loop 
of Henle. .Before reaching the apex of the pyramid, the 
tubule turns and forms the loop of Henle, and, moving up- 
ward in a direction parallel to the descending loop, forms 
the ascending loop of Henle ; it again enters the cortex, form- 
ing the zigzag tubule ; becomes more contorted, forming the 
second convoluted tubule, joining a straight or collecting 
tubule, which passes through the medullary portion, and 
unites with other collecting tubules to form an excretory duct 
{duct of Bellini) that opens into the apex of the pyramid, 
through which the secreted urine may pass into the pelvis of 
the kidney. 

The different parts of the tubule differ very much in the 
kind of the epithelium lining them. In the epithelium we 
recognize three varieties: (1) granular cubical cells, having 
a fibrillated or rodded structure, as in the first convoluted 
tubule, spiral tubule, ascending loop of Henle, zigzag tubule, 
and second convoluted tubule; (2) clear cubical in the de- 
scending loop of Henle, and straight collecting tubule; (3) 
in the capsule squamous epithelium reflected over the glom- 
erulus, there being thus two layers, the inner of which is 
fused with the glomerular loop. 

It is believed that the cells of the convoluted and irregular 
parts of the tubules are secreting in their function; as they 
exhibit the character of active secretive cells, they are there- 
fore probably concerned with the extraction from the blood 
of the chief organic substances of the urine. The cells of 
the collecting and discharging parts of the tubule are like 
those seen in the conducting portion of other glands, and 
probably have no secreting function. 

The kidney is a highly vascular organ. The renal artery 
enters it as a direct branch from the aorta, entering the kid- 
ney at the hilum, dividing on entering the pelvis into several 



THE URINE. 355 

pyramids in the columns of Bertin. When they reach the 
boundary between the cortical and medullary portion, these 
branches spread laterally from incomplete anastomosing 
arches at the bases of the pyramids; from these arches 
some branches proceed outward toward the cortex and inward 
to the medullary pyramids. The vessels in the cortex between 
the medullary rays are called the interlobular arteries. The 
arteries in their outward course give off lateral branches that 
form the afferent vessels of the Malpighian bodies, forming 
the glomerulus (Fig. 149). From each granular tuft some- 
what smaller efferent vessels pass out of the capsule, and 
again break up into a network of capillary vessels over and 
between the tubules. !Note here the double capillary network 
somewhat resembling that of the liver. The arterial branches 
which go to the medullary substance in a straight direction 
through the pyramids are called the arteria? rectos, and these 
break up into a plexus of capillaries with elongated meshes 
from which the venae recta? are given off, which form into 
venous arches, corresponding to the arterial arches at the 
boundary of the cortex and medulla. The capillaries from 
the Malpighian bodies unite to form the interlobular veins, 
which empty into the venous arches. 

The small veins at the surface of the cortex are arranged 
in a star-shaped manner, and are called the venae stellatae. 
The lymphatics of the kidneys arise in the lymph spaces of 
the connective tissue of the organ, and form into vessels 
which leave the kidney at the tubes or through the capsule. 
The nerves of the kidney are derived from the renal plexus 
and lesser splanchnic nerves, and form small trunks with 
ganglia. 

The Urine. — Fresh urine is of a clear straw color, of a 
peculiar odor, and an acid reaction. It consists of water hold- 
ing in solution urea and other solids, and has a normal spe- 
cific gravity of 1.02 on the average, but is subject to varia- 
tion from this average within certain limits, the specific 
gravity corresponding to the proportion of the solids to that 
of the water; thus it may range from 1.002 after drinking 



356 THE KIDNEYS. 

much water, to 1.040 after abstinence from drinking fluids, 
or after copious perspiration. Any cause that tends to 
remove large quantities of water from the body through 
other channels than that of the kidney, as through the skin, 
the lungs, or bowels, lessens the proportion of water in the 
urine and increases its specific gravity, as the amount of 
solids discharged from the kidney remains, in normal con- 
dition, quite constant. The activity of the epithelium of the 
tubules will also influence the specific gravity by increasing 
or lessening the proportion of water. 

Climatic conditions have a marked influence, as when 
it is cold and the amount of perspiration is scanty, the 
amount of urine is increased, as well as being more diluted 
than when the perspiration is copious. From this it will 
be easily seen why persons inclined to kidney troubles or suf- 
fering from them should seek warm climates, or at least keep 
the body well clothed and the skin active. 

In the adult, the normal average amount of secretion daily 
is about fifty fluid ounces, or two and one-half pints. The 
percentage composition is as follows: Water, 96.7; solids, 
33, of which the more important are urea, 1 14.2; uric acid 
and other nitrogenous substances, 10.63; salts, 8.13, the 
more important of which are sulphates, phosphates, chlorides 
of sodium and postassium, and occasionally lactates, oxalates, 
hippurates, and acetates. 

The acidity of the urine is not due to the presence of 
free acid, but to acid-sodium phosphates. On standing in 
contact with the air, the urine becomes alkaline, due to the 
conversion of urea into ammonium carbonate, the decompo- 
sition being due to the presence of micro-organisms. The 
color of the urine is due to certain pigments of whose nature 
We are in doubt, but by some physiologists the chief coloring 
matter is considered to be urobilin, which is probably derived 
from the bile pigments. 



iThe urea contains from 83 to 86 per cent of the nitrogen of the urine; 
ammonia from 3 to 4 per cent, and uric acid and kreatin, xanthin, etc., the 
remainder of the nitrogen. 



EXCRETION OF THE URINE. 357 

Urea, one of the most important constituents of the urine, 
is the chief end-product of proteid metabolism. Its produc- 
tion is much more complex than the formation of carbon 
dioxide or water. 

Excretion of the Urine. — The excretion of the urine is 
now ffenerallv thought to consist of two or more distinct 
processes: (1) of filtration, by which water and the ready- 
formed salts are taken from the blood by the action of the 
Malpighian corpuscles by the renal glomeruli; (2) of true 
secretion, which takes place in the tubuli uriniferi, which 
separate from the blood the urea and like substances. 

Passage of the Urine into the Bladder. — There are three 
influences which work together to effect the passage of the 
urine from the kidney: (1) gravity, (2) the high pressure 
under which it is secreted, (3) the rhythmical peristaltic 
contraction of the ureters. 

The Ureters. — The ureters are the tubes which lead from 
the kidney to the bladder, one entering on each side, near 
the base of the bladder (Fig. 6). They are from sixteen to 
eighteen inches long, and about the diameter of a goosequill. 
They are composed of an outer fibrous coat of connective 
tissue containing blood vessels and nerves, a middle mus- 
cular coat of longitudinal and circular unstriped fibers, and 
an inner mucous coat made up of several layers of stratified 
transitional epithelium. The ureters enter the bladder 
obliquely so as to form a sort of valve to prevent the reflux 
of the urine from the bladder. 

The Bladder and the Urethra. — The organ for the retention 
of the urine until excreted from the body is the bladder. It 
is situated in the pelvic cavity, and has an average capacity 
of twenty fluid ounces. Its structure resembles the ureters, 
but it has thicker mucous and muscular coats. 

From the neck, or narrow end of the bladder, there passes 
a tube (the urethra) by which the urine is expelled from the 
body. At its beginning the circular nonstriated muscular 
fibers become thicker, but the opening is closed by a sphincter 
muscle (sphincter urethra?), of striped muscle fibers, which 



358 THE KIDNEYS. 

by its tonic contraction keeps the opening closed, and by its 
relaxation permits the urine to pass into the urethra. 

The expulsion of the urine is produced by the gradual 
accumulation of the urine, producing a tension in the organ, 
bringing about a contraction of the muscular walls and a re- 
laxation of the sphincter. In young children the whole act is 
reflex. As age advances, there is acquired more or less control 
of the act ; the will may send a stimulus which inhibits the 
reflex movement and assists the sphincter, preventing expul- 
sion, or it may inhibit the sphincter, and by stimulus to the 
abdominal muscles, aid in the expulsion. 

Conditions Affecting the Secretion of the Urine. — The 
more important conditions affecting the secretion of the urine 
are: — 

1. The blood pressure. The more blood in the renal 
artery, the greater its secretion. This increased pressure may 
arise (a) from an increase in the force or frequency of the 
heart beat; (b) from a dilation of the blood vessels of the 
kidneys through the action of the vasomotor nerves; and (c) 
by constriction of the small arteries of other areas, as that of 
the skin. 

2. By the nervous system independent of the action of the 
vasomotor nerves. We know little as to how this is effected. 

3. By certain substances (diuretics), as water, sodium 
chloride, sodium and potassium nitrate, caffein, grape sugar, 
digitalis (foxglove), and alcohol. 

Effect of Alcohol on the Kidneys. — As alcohol increases 
the force and frequency of the heart beat, and as it also causes 
a dilation of the blood vessels through its action on the vaso- 
motor nerves, it will be readily seen why its habitual use will 
prove very injurious to the kidneys, resulting, by its con- 
tinued disturbance (congestion) of the renal circulation, in 
albuminuria 1 and Bright's disease. 



i High living or an excessive use of iced tea or ice-water may produce al- 
buminuria. Colds are one of the most fruitful sources of acute Bright' s disease. 
Formerly Bright's disease was used as a synonym of albuminuria, but this is not 
a correct use of the term, as this is a different disease. While albumin is in 
excess in Bright's disease, Bright's disease does not accompany albuminuria. 



CHAPTER XV. 

DUCTLESS GLANDS. 
EXPERIMENTS AND DEMONSTRATIONS. 

1. Remove the muscles from the neck of a rabbit or a 
cat, and watch carefully for a glandular organ (the thyroid 
gland), reaching from the thyroid cartilage down the sides 
of the trachea, the lateral masses being connected by a nar- 
row strip of glandular substance. Look carefully for similar 
masses (accessory thyroids), distributed in various parts 
of the neck, and even as low down as the heart. Do you 
find in any of these glands any evidence of a duct ? Make a 
section of different portions, and examine under low power 
(twenty or thirty diameters), and carefully note general 
structure. Make permanent mounts of different portions as 
directed in Appendix. Examine under two-thirds and one- 
sixth objectives. What evidence do you see that the gland 
has a secretion ? 

2. Examine the cap-shaped body (suprarenal capsule) 
on the upper part of the kidney. Does it have any connec- 
tion with the kidney ? Has it any duct ? Determine its 
microscopic structure. What evidence have you that it has a 
secretion ? 

3. Remove the brain from its cavity, and take special 
care not to injure the lower portion in the region of the 
sphenoid bone. Xote this part of the brain, and look for a 
reddish gray body (pituitary body) covered by the folds of 
the pia mater. Of how many lobes does it consist ? Do these 
lobes differ in structure ? Examine under both high and 
low powers. Is the body vascular ? 

4. In a brain that has been hardened in alcohol or synthol 
find the pineal gland, and study its relations and structure. 
What evidence do you find that it is the vestige of a once 
functional organ ? 

5. Examine the spleen, and determine its relation, blood 
supply, and microscopic structure. Has it any resemblance 
to a lymphoid gland ? Does it have the structure of a secret- 
ing gland ? 

359 



360 DUCTLESS GLANDS. 



DUCTLESS GLANDS. TEXT. 



Importance — Until recent years, these glands were 
looked upon as the remnants of once functional glands, now 
playing no important part in the work of the adult organ- 
ism, and therefore of little importance. The fact that the 
removal of these organs produces a great disturbance in the 
healthy action of the body, and in some cases causes death, 
has given a new interest to their study, and has resulted in 
the discovery of some very important physiological facts. 
While we are still in doubt as to their full importance, it is 
well established that most of them are more than mere rudi- 
ments of organs, and, while they have no secretions to give 
off, most of them have internal secretions which have very 
important functions. To this group of glands belong the 
suprarenal capsule, the thyroid gland, thymus gland, the 
pituitary tody, the pineal gland, coccygeal glands, carotid 
glands, and spleen. While the liver and the pancreas are not 
ductless glands, they are related to them by virtue of their 
internal secretions, and need mention in this connection. 

Internal Secretion. — In most of these glands the paren- 
chyma cells are morphologically of the secretory type, and 
as active constituents have been extracted from them, we are 
safe in assuming that they produce a secretion. As they 
have no ducts, these secretions, whatever their nature or 
quantity, pass directly into the blood (as in the suprarenal 
capsule), or indirectly into the blood by means of lymphatics 
(as in the thyroid), and as they do not pass to a free surface 
by means of a duct, as in the salivary and other glands, their 
secretion is called internal secretion. 

Thymus Gland — When at its full development, it is a 
long, narrow body situated in the front of the chest, behind 
the sternum, and reaching upward to the lower part of the 
neck. It has well-marked lobes, and is of a reddish or gray- 
ish color. It has a fibrous capsule, which sends off numerous 
processes, which divide the gland into numerous lobes, and 
a well-marked cortex and medullary portion ; and it contains 



THE THYROID GLAND. 361 

a large amount of adenoid tissue, with numerous lymphoid 
corpuscles in the cortex. 

After the second year it begins to diminish, and by adult 
age there is only a small vestige remaining, and it may, 
therefore, be looked upon as a rudimentary organ. It gives 
numerous extractives. 

It is supposed to be the " parent source from which all 
the red corpuscles are derived/' and hence its large size in 
the young child. It is thought that the first red corpuscles 
are developed from the thymus gland, and from these the 
others are formed. 

Thyroid Gland. — It is situated in the neck. It is made 
up of two lobes which lie on both sides of the trachea, reach- 
ing upward to the thyroid cartilage and connected in front 
by a smaller middle lobe. It is a very vascular organ, and 
of variable size in different individuals. It is covered by a 
dense capsule of areolar tissue, which sends off branches in- 
closing vesicles containing colloid material, the vesicles being 
lined by a single layer of short cylindrical or cubical cells. 

The colloid substance of the vesicles is believed to be the 
secretion of these glands. This secretion finally ruptures 
the vesicles containing it, and finds its way to the lymph, and 
by the lymph to the blood. 

The complete removal of the thyroid gland in some ani- 
mals produces death. In man its removal produces a disease 
called mucous dropsy (myxcedema). The disease is cured 
by the injection of the extract of the secretion from the 
thyroid of the sheep. 

The Suprarenal Capsules — These are two cap-shaped 
bodies (Fig. 6) situated on the super and outer part of the 
kidney. They are invested by a capsule of connective tissue, 
which sends off very fine prolongations into the substance of 
the gland. The gland is made up of medullary and cortical 
portions. The gland is richly supplied with nerves. The 
fibers enter through the hilum of the gland, but the method 
of the termination has not been determined. If one gland 
is removed, the other increases in size (hypertrophies). 



362 DUCTLESS GLANDS. 

The results from experiments with the gland seem to 
indicate that the gland is essential to life ; and its destruction 
by disease produces symptoms similar to those of Addison's 
disease. The giving of suprarenal extractive in such cases 
has proved beneficial. 

Internal Secretion of the Pancreas.— Within a few hours 
after the t6tal removal of the pancreas, sugar makes its ap- 
pearance in the urine, reaching as high as ten per cent, 
and death generally follows in fifteen days or less. If por- 
tions of the gland be left (at least one tenth), sugar only 
appears in the urine when carbohydrates are eaten, but not 
otherwise. This effect is not due to the normal secretion of 
the pancreatic juice, as this may be entirely removed without 
producing the effects described. The existence of an internal 
secretion has not been established, and we do not know the 
cause of the injurious effect of removal of the organ. Its 
power to prevent the formation of sugar is, however, estab- 
lished. 

The Spleen. — The spleen (Fig. 126) is a ductless organ, 
and the largest of the vascular organs, but it has probably 
no internal secretion. The functions of the spleen have been 
given under the subject of alimentation. The spleen may 
be removed without any marked injurious effects. 

The Pituitary Body. — This small, reddish-gray body lies 
in a depression (sella turcica) of the sphenoid bone. It con- 
sists of a small posterior lobe of nervous tissue and an anterior 
larger lobe of tissue resembling the thyroid gland. These 
two lobes are not only histologically different, but are also 
embryologically distinct. 

The function of the organ is not known. By some its 
function is thought to be similar to that of the thyroid gland. 
In case of disease of this organ there has come to be associated 
with it a disease (acromegaly) in which there is an abnormal 
increase in the size of the extremities of the bones. 

The Pineal Gland. — This gland is situated beneath the 
back part of the corpus callosum, and rests upon the corpora 
quadrigemina. It is a small body of reddish color. 



CAROTID AND COCCYGEAL GLANDS. 363 

It has a central cavity lined with ciliated cells. Its 
glandular substance is made up of an outer cortical substance 
resembling in structure the outer lobe of the pituitary body, 
and an inner central layer of nervous substance. The pineal 
gland is considered as a purely vestigial structure, being an 
atrophied third eye and without any important function in 
the human subject. It is of morphological interest to the 
scientist in that it is a good example of the principle that 
organs, when they cease to be functional, become reduced in 
size and structure. 

The Carotid Glands. — These are situated at the branch- 
ing of the common carotid artery, on each side. They are 
composed of a plexus of small arteries, inclosed and sup- 
ported by a covering of connective tissue, in which there are 
numerous connective tissue corpuscles. Surrounding the 
blood vessels are one or more layers of cells, resembling 
secreting cells, probably derived from the plasma cells of 
the connective tissue. 

The Coccygeal Glands. — These are situated in front of 
the tip of the coccyx. They have the same structure as the 
carotid glands. The function of these glands is not known. 



CHAPTER XVI. 

GENERAL AND SPECIAL SENSES. 
EXPERIMENTS AND DEMONSTRATIONS. 

1. To determine the cold spots on the arm. Take a sharp 
pointed piece of ice, and touch different parts of the bare 
arm. What parts are the most sensitive ? 

2. Determine the hot spots of the arm by touching dif- 
ferent parts with a pointed copper instrument dipped in hot 
water. Do the hot areas agree with those of the cold areas ? 

3. Determine which gives the clearer sensation, light 
pressure or heavy pressure. 

4. Test, by means of a blunt pointed compass, various 
parts of the body as to which is the most sensitive to touch. 
Place the compass points together, then gradually separate 
them until you can distinguish the two points. Which parts 
of the body are the more sensitive ? 

5. Place two light weights, one cold and the other warm, 
on corresponding fingers of the hand. Which is the heavier ? 

6. Place the hands in cold water, then in tepid water, 
then in warm water. Reverse the process. What difference 
do you note ? Is our sense of temperature absolute or rela- 
tive? 

7. Cross the middle finger over the index finger; roll 
a small marble between the tips. How many marbles do 
you seem to feel ? Cross the fingers in the same way, and 
rub the point of the nose. How many noses do you seem 
to feel? 

8. Put a drop of vinegar on a friend's tongue, and, with 
a reading glass, notice how the papillae of the tongue start up. 

9. Rub different parts of the tongue with a piece of 
gum-aloes. What parts seem to be most sensitive to bitter ? 
Try the same with a piece of salt, and determine what parts 
are most sensitive to saline substances. 

10. Try the sensitiveness of the tongue with sweet sub- 
stances and with sour substances. How do the dorsum of 
the tongue and the edges compare in sensitiveness ? 

364 



QUALITIES OF SENSATION. 365 

11. It ub the tongue with the pulp of a ripe apple, and 
close the nostrils. Does it affect the taste when the nostrils 
are closed ? Rub the tongue with a piece of onion, keeping 
the nostrils closed. Close the eyes, and try the experiment. 
Can you tell the apple from the onion ? What does this 
teach you in regard to flavor ? To what is the taste of cof- 
fee most due ? 

12. Taste various substances with the eyes closed. Ex- 
plain the difference. 

13. Place pieces of zinc on the tongue, also beneath and 
above the tongue, and have their ends brought into contact; 
an acid taste is produced due to the feeble galvanic currents. 

PAIX AXD COMMOX SEXSATIOX. TEXT. 

Common sensation, or general sensibility, seems to arise 
from a number of obscure sensory impulses proceeding from 
the skin and other parts of the body, and by these sensa- 
tions we have a more or less perfect knowledge of our general 
condition. If these impulses become intense, the sensation 
is called pain, so we may consider pain as an excessive stimu- 
lation of the nerves of common sensation; but pain is not 
restricted to the nerves of general sensation, for excessive 
stimulation of any sensory nerve produces pain. Since every 
kind of overstimulation — mechanical, thermal, chemical, or 
electrical — may excite pain on the surface of the body, pain 
may be considered as a cutaneous sensation. It is, however, 
found in almost all other organs. A slight inflammation 
makes an organ keenly sensitive to pain. Pain may be 
caused by the stimulation of a sensory nerve along any part 
of its course, but the sensation is referred to the nerve ter- 
mination. 

Pains vary in intensity and quality with the nature and 
strength of the stimulus and the excitability of the nerve 
affected. If very violent, the sensation seems to be diffused 
and scattered, so that localization is difficult. The sensations 
of common sensibility and pain are distinct from other sen- 
sations. In the common sensory nerves there is probably no 
special nerve ending, while in those of special senses each 
sense has its special end organ. 



366 GENERAL AND SPECIAL SENSES. 

There are three views held by physiologists in regard 
to pain: (1) that it is a special sensation provided with a 
special conducting apparatus in each part of the body; (2) 
that it is produced by an overstimulation of the special nerves 
concerned with touch or temperature, or of the other nerves 
of special sense; or (3) that it is an overstimulation of the 
nerve of common sensation which tells us both of the surface 
and internal organs of our bodies. 

While there seems to be evidence for each of these views, 
the evidence leads us to doubt the existence of special end 
organs for common sensation. 

We have learned that through the skin we may experience 
three classes of sensation : those of touch, of temperature, and 
of common sensibility, any of which may become painful by 
undue excitement. 

The question arises as to how these different sensations 
are produced lm 9 i. e., are they produced by the difference in 
the quality of the stimulation, or by the difference in the 
nerve endings capable of taking notice of these specific qual- 
ities ? 

From what has been learned from experiments and clinic 
experience, it appears that the skin has four kinds of nerve 
fibers for the four functions: pressure, heat, cold, common 
sensibility or pain. Whether each of these fibers has distinct 
terminal endings has not been determined, and the degree 
to which each is differentiated is also in doubt. 



i There is little doubt that the sensory nerve trunks contain functionally 
different nerve fibers. The following are some of the evidences supporting this 
view: (1) In some diseases of the nerves, touch in certain parts of the skin has 
been lost, while the power to determine temperature remains, and vice versa. 
(2) In other cases, common sensibility and pain have been lost over certain areas, 
while touch has remained; and, in general, it may be stated that one or another 
class of cutaneous sensations may be lost while others remain. (3) The conduct- 
ing fibers for these sensations take, to a great extent, different paths in the 
spinal cord, and have different central endings. (4) From the varied power of 
the skin, the appreciated various degrees and varieties of tactile sense would 
seem to indicate that these different fibers have distinct functions. (5) That the 
hot spots do not coincide with the cold spots would seem to show that there are 
portions of the skin which have nerves that are sensitive to cold and not to heat, 
and also the converse seems to imply that there are special nerve fibers for the 
different temperature sensations. 



ORGANS OP TOUCH. 367 

Organs of Touch. — The sense of touch is not confined 
to particular parts of the body as are the other senses, but 
all parts capable of perceiving the presence of a stimulus 
by ordinary sensation are, in a certain degree, the seat of 
this sense. We should not, however, consider touch a mere 
modification of common sensation or sensibility. All parts 
of the body supplied with sensory nerves are thus in some 
degree organs of touch, but the sense is exercised in its per- 
fection only in those parts provided with abundant papillae, 
and in which the mucous membrane or skin is very thin, as 
in the tongue and the lips. The teeth and nails each possess 
a peculiar and acute sense of touch. The hair may also be 
reckoned an organ of touch, as in case of the eyelashes. 

Cutaneous sensations are of various kinds: (1) those of 
tactile sensation, or touch proper; (2) thermal sensations, 
Or sensations of heat and cold, and (3) sensation of pain. 
Before considering this matter at length, let us notice the 
kinds of end organs concerned in the sense of touch. 

End Organs. — These are of four kinds : — ■ 

1. Free Nerve Endings. — In all parts of the epidermis 
and in the cornea fine nerve fibrils are found derived from 
the splitting up of the axis-cylinder of a single nerve passing 
upward from the underlying dermis, the free ends of whose 
fibrils are sometimes provided with small swellings. Sim- 
ilar enlargements are found in the endings of the nonmedul- 
lated nerve fibrils in some parts of the body, and these are 
sometimes called touch cells. 

2. Tactile Corpuscles. — These are small, oval bodies 
(Fig. 150) averaging one three-hundredth of an inch in 
length, and one five-hundredth of an inch in breadth, situated 
in the papillae of the dermis. They are sometimes called the 
touch corpuscles of Wagner. They are most numerous in the 
palms of the hands, the soles of the feet, and especially in the 
fingers and toes; they are less numerous on the back of the 
hand, lips, and tongue, and are very few on the under surface 
of the arm and eyelids. 

In a large portion of the skin they are absent. Each 



368 



GENERAL AND SPECIAL SENSES. 



touch corpuscle consists of an outer covering of connective 
tissue arranged in transverse layers, within which is the 
core, showing elongated nuclei. Passing to the lower part 
of the core are one or more nonmedullated fibers which wind 
around it two or three times, and losing the sheath the fibers 
enter the interior of the corpuscle, the axis-cylinder ending 
in a small enlargement. 

3. End Bulbs. — These are also called organs of Krause. 

They are small 
oblong or rounded 
corpuscles from 
one three hundred 
and sixtieth to one 
one hundred and 
seventieth of an 
inch long. The 
axis - cylinder o f 
the nerve fiber 
passes into the in- 
terior of the cor- 
puscles, and ter- 
minates in a 
coiled mass or in 
a bulbous extrem- 
ity. It is invested 
by a capsule of 

ing in epidermis. 4. Simple papilla. Connective tissue, 

with a core of granulated material and nerve sheath of Henle, 
with the neurilemma appearing to become continuous with 
capsule. They are only found in the conjunctiva of the eyes, 
in the mucous membrane of the lips, in the tendons, and in 
some other parts of the body. 

4. Pacinian Corpuscles. — The Pacinian bodies, or the 
corpuscles of Yater, as they are sometimes called, are small 
elongated oval bodies found on some of the cerebrospinal and 
sympathetic nerves, especially in the cutaneous nerves of 
the hands and feet, on branches of the large sympathetic 




Fig. 150. — Tactile Corpuscle. 
Tactile corpuscle. 2. A touch cell. 3. Nerve end- 




PLATE XV. 
Fig. 131 — Arteries. 

1. Aorta. 2. Descending aorta. 3. '"celiac axi«. 24 Gastric artery. 25. Splenic artery. 23 
Hepatic artery. 26. Renal artery. 27. Mesenteric artery. 4. Abdominal aorta. 5. Lett com- 
mon iliac. 6. Femoral artery. 7. Popliteal artery. 8- Posterior tibial artery. 9. Anterior 
tibial artery. 12. Right innominate artery. 13. Right subclavian artery. 14. Brachial artery. 
15. Ulnar arrery. 16. Hadial artery. 1^. Common carotid artdry. 19. Temporal artery. 20- Pul- 
monary artery. 21. Left branch of pulmonary artery- 

Veins. 

30. Descending vena cava. 31- Left innominate vein. 32. Right innominate vein. 33 Left 
subclavian. 34. Axillary vein, x. ( ephalic vein . 35. Radial vein. 36. Ulnar vein. 48- Thoracic 
duct. 49. Jugular vein. 50. Pulmonary vein. 37. Ascending vena cava. 38- Hepatic vein. 39- 
Portal vein. 40. Renal vein. 42. Gastric vein. 43 Mesenteric vein. 44. Right common ihac 
vein. 45. Femoral vein. 46. An. erior tibial vein. 47. Posterior tibial vein. 



TOUCH PROPER. 369 

plexus about the abdominal aorta, and quite often on the 
nerves of the mesenteries. In the mesentery of the cat they 
may be seen by the naked eye; they have also been found 
in the pancreas, lymphatic glands, and thyroid glands. 

Each corpuscle is somewhat oval in shape, large and 
more complex than the touch corpuscles or end bulbs. They 
are one tenth to one fifteenth of an inch long and one twen- 
tieth to one thirtieth of an inch broad. Each corpuscle is 
attached by a narrow pedicel to the nerve on which it is sit- 
uated. It is composed of several concentric layers of fine 
membrane made up of a hyaline ground membrane with con- 
nective tissue fibers, each layer being lined with endothe- 
lium; passing through each pedicel is a single nerve fiber 
which, after traversing the several concentric layers and their 
immediate spaces, enters a central cavity, and gradually los- 
ing its dark border becomes smaller and terminates at or near 
the distal end of the cavity, in a knob-like enlargement, or in 
a bifurcation. These bodies do not occur in the skin proper, 
but in the subcutaneous connective tissue of the palm of the 
hand and the sole of the feet, including the fingers and toes, 
along the nerves near the joint, etc. ; being thus deep seated, 
there is doubt as to their connection with cutaneous sen- 
sation. 

Touch Proper. — Of tactile sensation we recognize two 
varieties: (1) sensation of simple pressure and (2) sensation 
of locality. The mere contact of a body with the skin gives 
a slight sensation of touch, the sensation becoming more 
acute up to certain limits as the pressure increases. The sen- 
sitiveness to pressure varies in different parts of the skin. 
This is determined by allowing small weights to press on the 
skin of various parts, different weights being used, one after 
the other, and the sensation noticed. By this means it has 
been determined that the parts most sensitive to the pressure 
sense are on the forehead, temples, and on the back of the 
hand, which will detect a pressure of .002 of a gram. The 
skin of the finger detects a pressure of .005 to .015 of a gram. 

In feeling the pulse, where we wish to distinguish small 
24 



370 GENERAL AND SPECIAL SENSES. 

intermediate variations of pressure, it is better noted with 
the tips of the fingers than with the skin of the forehead. 

When the skin is touched by an object, we not only expe- 
rience a sensation of greater or less intensity varying with 
the pressure or the part receiving the pressure, but we are also 
aware of the part that has been touched. This latter power 
is called sense of space or locality. In this, as in the pressure 
sense, not all parts of the body are equally sensitive, nor do 
they correspond with those most sensitive to pressure. The 
acuteness of sense of space probably depends on the number 
of sensory nerves in the part affected ; for the fewer the fibers 
in a given area, the more likely it is that the adjacent points 
will act on only one and produce but one sensation, and the 
greater the number of fibers in a given area the more likely 
it is that the different points will be distinguished and 
the locality determined. The common mode of determining 
the sensitiveness of the various parts of the body is by plac- 
ing the two blunted points of a pair of compasses on a part 
of the skin, thus determining the smallest distance at which 
the two points are felt as one impression. From this it is 
found that the tip of the tongue is most sensitive, and the 
middle part of the forearm and the middle of the thigh is 
least sensitive. 

From a study of this subject it will be noticed that those 
parts are most sensitive in such parts of the body as carry 
out the widest and most rapid movements. The sensitive- 
ness is increased by moistening the skin, but a cold and 
bloodless condition of the skin blunts the sensibility. The 
sensitiveness is improved somewhat by exercise. But Mr. 
F. Galton says that the alleged superiority of blind persons 
in sensitiveness of touch is not great, as the guidance of the 
blind depends mainly on the multitude of collateral indica- 
tions to which they give heed, and not in their superiority 
in any one of them. 

Sensation of Temperature. — The skin, and certain parts 
of the mucous membrane are capable of temperature sensa- 
tion. These sensations are of two kinds: sensation of heat, 
and sensation of cold. They differ from each other, as well 



SENSATIONS OF HEAT AND COLD. 371 

as from the sensation of pressure. When we examine the 
skin, we find areas which are especially sensitive to heat, 
called hot spots ; there are also areas which are sensitive to 
cold, which are called cold spots. These areas do not always 
coincide, nor do they correspond with the points sensitive to 
pressure. The cold spots are more numerous than the hot 
spots. These spots are often arranged in lines somewhat 
curved. The areas are determined by a pointed pencil of 
copper, by dipping it into hot water and touching parts of the 
skin ; some parts will be found very sensitive to heat while 
others do not have this sensation. For determining the cold 
spots a pencil of ice is taken, by which it is found there are 
spots sensitive to cold, but not to heat. From this difference 
in sensation it would seem that these different spots have 
specifically different nerve fibers. 

The sensation of heat and cold can only be felt through 
the nerve endings of the skin. The direct stimulation of the 
nerve produces only a sensation of pain. 

It has been found that — 

1. Bodies of the same temperature, as the part of the 
skin to which they are applied, give rise to no thermal 
sensation. 

2. The parts of the body having the sense of temperature 
most acute are, in order, the tip of the tongue, the eyelids, 
the cheeks, the lips, and the hands. 

3. Small differences of temperature about two-thirds C. 
are readily appreciated by the sensitive parts when the tem- 
perature lies near that of the body. 

4. The power of the skin to recognize changes of temper- 
ature is very great, yet our power of estimating absolute 
temperature by skin sensations is small. Our own feeling 
of warmth depends on the state of the cutaneous blood vessels, 
full blood vessels causing us to feel hot, and empty vessels to 
feel cold. Hence an object at the same temperature will pro- 
duce upon us different sensations of temperature, accordingly 
as the skin is full or empty of warm blood. 

5. Illusions in this sense are common: a cold weight is 
heavier than a warm one ; a good conductor, like metal, feel- 
ing colder than a piece of wood of the same temperature. 



372 



GENERAL AND SPECIAL SENSES. 

THE SENSE OF TASTE. 



Organs of Taste The principal seat of the sense of 

taste is the tongue (Fig. 151). We know from common ex- 
perience and from experiments that this sense also resides 
15 16 




Fig. 151. —The Tongue. 
1. Lymphatic gland. 2. Arch of pharyngqpalatal muscle. 3. Tonsils. 4. 
Glossopalatal muscle. 5. Coecal foramen. 6. Oircumvallate papilla. 7. Tongue. 
8. Exterior maxillary artery. 9. Masseter muscle. 10. Cut end of maxillary 
bone. 11. Maxillary foramen. 12. Internal pterygoid muscle. 13. Digastric and 
stylopharyngeal muscle. 14. Parotid gland. 14. Internal jugular vein. 16. In- 
ternal carotid artery. 17. Epiglottis. 

in the soft palate and in its arches, in the uvula, tonsils, and 
probably the upper part of the pharynx. 

These parts, together with the base and posterior part of 
the tongue, are supplied with branches of the glossopharyn- 
geal nerve. In most persons the anterior parts of the tongue, 
especially the edges and tip, possess the sense of taste. There 



THE SENSE OF TASTE, • 373 

are persons who do not seem to be able to taste with these 
parts. 

The middle of the dorsum of the tongue has only feebly 
the power of taste, due probably to the density and thickness 
of the epithelia which prevent the sapid substance from pene- 
trating to their sensitive parts. 

The Tongue. — The tongue is a muscular organ covered 
with mucous membrane. By its base, or roots, it is attached 
behind with the hyoid bone, with the epiglottis, and with the 
fauces. Its under surface is connected below with muscles 
which form the floor of the mouth. Under the tongue, the 
doubling of the mucous membrane forms the frcenum. A 
fraenum is also found within each lip, at its middle, and one 
in front of the epiglottis. 

The tip and dorsum of the tongue are free. The muscles 
which form the greater part of the substance of the tongue 
are called the intrinsic muscles; these are attached to the base 
of the mucous membrane, chiefly, and it is by them that the 
smaller or more delicate movements are chiefly performed. 
The muscles by which the tongue is fixed to the surrounding 
parts, and by which its greater movements are performed, 
form what are called the extrinsic muscles. The mucous 
membrane of the tongue, for the greater part, is similar in 
structure to the membrane as found in other parts of the 
body, except on the dorsum of the tongue, where its structure 
is similar to that of the skin, consisting of a corium having 
papillary and superficial epithelial layers. In structure the 
corium is very much like that of the skin, but is thinner and 
less compact. It serves as a place of insertion of the muscle 
fibers of the tongue. On the under surface of the tongue the 
mucous membrane is thin and smooth. The convex dorsum 
of the tongue is marked by a slight furrow, or raphe, along 
the middle line, that ends in a depression called the ccecal 
foramen (Fig. 151). 

Papillae of the Tongue. — The mucous membrane of the 
upper surface is covered by large papillae, which give to it a 
rough appearance. These consist of two kinds, the simple 
and the compound. The simple papilla? are like those 



374 



GENERAL AND SPECIAL SENSES. 



found in the skin, and are distributed over the whole surface 
of the dorsum of the tongue between the compound papilla. 
They are most numerous in its posterior portion. 

Of the com- 
pound papillae 
there are three 
varieties : the 
papillae m a x - 
imae, or circum- 
vallate; the 
papillae media?, 
o r fungiform; 
and the papillae 
minimse, or 

filiform. 

The circum- 

vallate (Fig. 
151) are ar- 
ranged in two 
rows, diverging 
forward from 
the middle o f 
the back of the 
tongue i n t h e 
form of a V. 
They are ten or 
twelve in num- 
ber, and are one 
twentieth to 
one twelfth of 
an inch wide. 
Each papilla 
consists of a 
circular projection having a broad, free surface smaller at the 
base, and surrounded by a narrow trench, or fossa, on the out- 
side of which the mucous membrane is raised to form a wall 
or velum. The substance of the papilla is made up of corium, 
or dermis, formed of dense connective tissue containing blood 




a b A c 
Fig. 152 A.— Papilla of the Tongue. 

A. Vertical section near the middle of the upper surface 
dorsal) of the tongue, a. Fungiform papilla, b. Fili- 
form papillae. Note the hair-like processes, c. Filiform 
papillae with epithelium removed and magnified two 
diameters. B. Filiform compound papillae, a. Artery. 
v. Vein. c. Capillary loop of the secondary papillae, b. 
Basement membrane, d. Secondary papillae deprived of 
e, e, the epithelium. /. Hair-like process of epithelium 
capping the simple papillae, magnified twenty-five diam- 
eters, g. Separated epithelial cells, magnified 300 diam- 
eters. 1, 2. Hairs found on the surface of the tongue. 3, 4, 5. 
Ends of hair-like epithelial processes, showing modes of 
imbrication of particles, but in all a coalescence of the 
particles toward the point. 5. Incloses a soft hair, mag- 
nified 160 diameters. (After Todd and Boman.) 




THE SENSE OF TASTE. 375 

vessels and nerves and covered by stratified epithelium. On 
the papilla are found smaller or secondary papilla?. In the 
epithelium of the sides of the papilla? are found small oval or 
flask-shaped bodies called taste buds, or taste bulbs (Fig. 152). 

The fungiform papillae are scattered over the surface of 
the tongue, but are most numerous at the sides and front. 
They are club-shaped, have a narrow base, and are of a bright 
red color, due to their rich supply of blood. 

The conical, or filiform, the most numerous of the papilla?, 
are scattered over 
the whole surface of 
the tongue, especially 
over the middle of 
the dorsum. They 
vary in shape, but, 

for the most part, Fig. 152 B.— Vertical Section of the Oircum- 

-1 £-1. vallate Papilla. (From Kolliker.) 

are COnical, 01' Ull- A% The p apilla3 . B. The surrounding wall, a. The 
form T U p v ,, a epithelial covering, b. The nerves of the papilla and 
luim. -L ll t: j die wa n spreading toward the surface, c. Secondary 

covered by a thick papillJB ' 

layer of epidermis, which is arranged over them, either in 
an imbricated manner or prolonged from their surface in 
the form of fine, stiff projections, hairlike in appearance, 
and in some cases in structure also. It would seem from 
their peculiar structure that they probably have a mechan- 
ical function, or one allied to that of touch rather than that 
of taste. This latter function is probably seated in the cir- 
cumvallate and the fungiform papillae, especially. 

Taste Buds. — These (Fig. 153) are found in the epithe- 
lium, on the lateral surfaces of all the circumvallate papilla 1 , 
in the epithelium of the surrounding velum, in many fungi- 
form papilla?, and in different parts of the general mucous 
membrane of the tongue, on the under surface of the soft 
palate and epiglottis. They are oval clusters of epithelial 
cells, lying in the epithelium and set vertically to the surface, 
having their broad base resting on the dermis portion of the 
mucous membrane and their neck opening at a pore on the 
surface. In each bulb, or bud, is found two kinds of cells : gus- 
tatory cells and supporting (sustentacular) cells. The former 



376 



GENERAL AND SPECIAL SENSES. 



are small spindle-shaped cells having a central nucleus with 
an outer process passing from one end to terminate as a fine 
hair that projects through the gustatory pore, and an inner 
process which is thought to be continuous with a nerve fibril. 
The fibril, in fact, may be considered as having its origin in 
the gustatory cell like a similar arrangement found in the 
organ of smell. The supporting cells are long and flattened 
with tapering ends. They are situated between the gustatory 
cells, and also form a kind of covering for the taste buds. 
<, These end buds, by 

means of the gustatory 
cells, form the end 
organs of taste. We are 
led to believe this from 
their connection with 
the fibers of the glosso- 
pharyngeal nerve, and 
from the fact that the 
sense of taste is chiefly 
found where they are 
most abundant, and 
that their cells resemble 
those of sensory epi- 
thelium. There are, 
however, portions of the 
tongue which have the 
power of taste, in which there are no fibers of the glosso- 
pharyngeal, but which are supplied by fibers from the 
fifth cranial nerve. The lingual branch of the fifth nerve 
is therefore considered as gustatory in its functions. There 
are filaments from the chorda tympani nerve which seem to 
have close connection with the sense of taste, as is shown 
from its destruction, producing loss of taste on the same side 
of the tongue; but its exact connection is but imperfectly 
understood. 

The various tastes seem to have specific nerves for dif- 
ferent parts of the tongue, and each is more sensitive to a 




Fig. 153.— Taste Bulb. 
1. Depression over goblet. 2. Hair process 
of taste cells. 3. Nucleus of taste cell (gusta- 
tory). 4. Incasing cells. 






THE SENSE OF TASTE 377 

certain taste tnan are the others. The back of the tongue is 
especially sensitive to bitter; the tip, to sweet and salt; the 
sides, to acids ; and the middle is almost devoid of taste sen- 
sation. Weak electric currents applied to the tongue give 
rise to different kinds of sensations in different parts of the 
tongue. Cocaine applied to the tongue in increasing doses 
destroys sensitiveness of all kinds in the following order: 
general sensation and pain, bitter taste, sweet taste, salt taste, 
acid taste, and sense of touch. 

Among the most clearly denned tastes are those of sweet 
and bitter, the acid and alkaline, salt and metallic tastes. 
Acid and alkaline tastes may be excited by electricity. 

The delicacy of the sense of taste is sufficient to discern 
one part of sulphuric acid in 1,000 of water, but in its 
acuteness it cannot compare with the sense of smell. While 
the taste apparatus is bilateral, the sensation or perception is 
single. In this respect taste resembles vision. Much of the 
perfection of the sense of taste is often due to sapid sub- 
stances being odorous, and thus exciting simultaneous action 
of the senses of smell and taste. This is shown by the im- 
perfection of the taste of such substances when action of the 
olfactories is prevented by a cold or by closing the nostrils. 

After Taste. — Very distinct sensations of taste are fre- 
quently left after the substances which excited them have 
ceased to act on the nerve ; and such sensation often lasts for 
a long time and modifies the taste of sweet substances tasted 
afterward. For example, the taste of sweet substances im- 
pairs the flavor of wine; the taste of cheese improves 
it. There appears to exist a similar harmony between taste 
as is found between colors; those that are opposed or com- 
plementary render each other more vivid, although we have 
not been able to formulate any general principle governing 
this relation. In the art of cooking, however, attention is 
given to this consonance of flavors. 

Conditions Necessary. — Substances to be tasted must be 
(1) either in solution or be soluble in the moisture covering 
the tongue ; for this reason insoluble substances are generally 



378 GENERAL AND SPECIAL SENSES. 

tasteless; (2) at a temperature of 37° to 40° C. (98° to 100° 
F.) ; (3) sentient surfaces. When the tongue and fauces are 
dry, a sapid substance, even in solution, is tasted with diffi- 
culty. 

Subjective Sensation of Taste. — The sense of taste may 
be excited by external cause, as changes in the conditions of 
the nerve centers, produced by congestion, or other causes 
which excite subjective sensations in the other organs of 
sense. We know but little on this subject, as it is difficult 
to distinguish the phenomena from the effects of external 
causes, such as changes in the nature of the secretions of the 
mouth. 

Other Functions. — Besides the sense of taste, the tongue, 
by means of its papilla?, has, especially at its sides and tip, 
a very delicate and accurate sense of touch, which renders it 
sensible to impressions of heat and cold, of pain, to me- 
chanical pressure, and to form of surface. It may lose its 
common sensibility, and still retain the sense of taste, and 
vice versa. While common sensation and taste may reside in 
the same papillae, the separate sensation may be received by 
different nerve fibers. 

Fatigue of Taste. — Like the other special senses, taste 
may become fatigued. The repeated tasting of one substance 
rapidly deadens the sensibility, due probably to" overstimula- 
tion. 

Modification of Sense of Taste. — Taste to a great extent 
is modified by hab^t, education, and other circumstances. 
Many articles we have to learn to like; as, tomatoes, olives, 
and, especially, tobacco. Articles of which we were very fond 
when young become unpalatable to us when older, and many 
things which we did not like when children we relish in older 
age. Certain conditions of the system produce craving for 
particular articles of diet. 



CHAPTER XVII. 



THE SENSE OF SMELL. 



The Organ of Smell. — The organ of smell is located in a 
portion of the mucous membrane lining the cavities that are 
situated between the base of the cranium and the roof of the 
mouth. 

The internal part is formed chiefly of two cavities called 
the nasal 
fossa?, open- 
ing in front 
into the air, 
by t h e nos- 
trils o r an- 
terior nares, 
and behind 
into the 
pharynx by 
the two pos- 
terior nares. 

The mid- 
dle wall of 
each fossa is 
formed by a 
vertical par- 




FlG. 154.- 



Nasal Fossa and Distribution of Olfactory 
Nerve. 
1. Olfactory nerve. 2. External twig of ethmoidal branch of 
nasal nerve. 3. Spheno-palatine ganglion. 4. Anterior pala- 
tine nerve. 5. Posterior, and 6, Middle, divisions of palatine 
nerves. 7. Region of inferior turbinated bones. 8. Branch to 
region of superior and middle turbinated bones. 9. Naso- 
11 Lion Willi a palatine branch to the septum. (As shown, the branch is cut 

smooth sur- short) 

face. The outer wall on each side is much convoluted. The 
upper portion, or roof, is formed by the cribriform plate of 
the ethmoid bone, from which a central vertical plate passes, 
and is continued downward by the vomer and by cartilage 
to form the partition between the nostrils, or anterior fossa?. 
The outer, or side, wall is formed, in part, by two scroll-like 



bones from the ethmoid, 



and, in part, by a third similar 
379 



380 



THE SENSE) OF SMELL. 



bone attached to the superior maxillary. By these three 
bones (turbinated bones) are formed the three passages called 
the superior, middle, and inferior meatus, and as we have 
learned in our study of the cranium, the passages have com- 
munication with small cavities, or sinuses, in the surround- 
ing bones. 

Mucous Membrane All of these cavities are lined with 

mucous membrane, which is continuous with that lining 
the pharynx, the Eustachian tubes, and the lachrymal 

canal to the 
eye. 

The nasal 
mucous, 
known as 
Schnei- 
der i a n 
membrane, 
differs in its 
structure in 
various 
parts. It 
may b e di- 
vided into 
three r e - 
gions: ( 1 ) 
the vestib- 
u 1 a r re- 
gion, (2) 
the respiratory region, and (3) the olfactory region. 

The vestibular region is at the entrance of the air pas- 
sages, whose mucous membrane contains numerous sebaceous 
glands and hair follicles from which stiff hairs, vibrissa!, 
spring. 

In the respiratory region is included the lower meatus, 
which is lined by thick mucous membrane with numerous 
mucous glands, and stratified ciliated epithelium. 

The olfactory region is the upper, and is the one especially 




Pig. 155. — Section through Nasal Fossa. 
1. Superior meatus. 2. Ethmoid cells. 3. Middle meatus. 
4. Maxillary sinus. 5. Inferior meatus. 



THE ORGAN OF SMELL. 



381 



connected with the sense of smell. It is formed of the an- 
terior two thirds of the superior meatus, the middle meatus, 
and the upper third of the septum (Fig. 154). In the 
dermis portion of this region there are numerous blood ves- 
sels and nerve fibers, also a large number of peculiar tubular 
glands having openings between the epithelial cells. The 
mucous membrane of the olfactory re- 
gion is soft and of a yellowish tint. The 
cells are of two kinds : those which are 
long and cylindrical, having a broad 
nucleated portion coming to the sur- 
face, and forked processes stretching to 
the corium, or dermis. These are called 
supporting, or sustentacular cells'; those 
which are long and spindle shaped hav- 
ing a nucleated central part, from which 
there passes to the surface a slender fila- 
ment, bearing a free cilium, while an- 
other filament passes down to the cor- 
ium, where it is lost among the nerve 
fibers, with one of which it becomes 
connected. 

The second variety of cells is called 
the olfactory, or rod, cells. Among the 
lower part of the other cells are found 
rounded cells, called basal cells (Fig. 
155). The nerve fibrils which are non- 
medullated at the base of the epithelium 
are distributed to the upper third, or 
olfactory region of the nose, and they have their origin in the 
olfactory bulb, passing through the cribriform plate of the 
ethmoid bone, upon which rests the olfactory bulb. These 
form the nerve of smell, and may be seen forming a brush-like 
expansion on the upper and middle turbinated bone, as well 
as on the septum, before they enter the mucous membrane to 
become connected with the olfactory cells, which are the real 
end organs of smell. The nose also receives nerve fibers from 




Fig. 156. — Olfactory 

Cells. 
1. Hair-like process of 
olfactory cell. 2. Their 
peripheral rods. 3. 
Their central filaments. 
4. Epithelial cells with 
deep branching pro- 
cesses. 



382 THE SENSE OF SMELL. 

the fifth cranial nerve, which are distributed to all parts of 
the mucous membrane. It has only the power of general 
sensibility, as is shown by only those parts being sensitive 
to odors which receive filaments to form the olfactory nerve ; 
and, further, the sense of smell may be lost while the sense 
of common sensation and pain remains. 

Conditions Necessary, — (1) The first condition is the 
presence of nerve and nerve-end organs, the changes in whose 
condition stimulate a special nerve center. A substance 
which excites the sensation of smell in the olfactory center 
may cause a peculiar sensation through the nerves of taste, 
and may produce an irritation and burning sensation on the 
nerves of touch ; but the sensation of odor is yet separate and 
distinct from these, though it may be perceived at the same 
time. (2) A substance to be perceived by smell must, in case 
of air-breathing animals, either be solid in a state of extreme 
division in the air, or in a gaseous condition, and must be 
soluble in the mucus of the mucous membrane ; consequently 
the mucous membrane must be moist in order to exert this 
kind of sensibility, as is shown by the impairing or loss of 
smell when the Schneiderian membrane is dry. (3) In air- 
breathing animals it is necessary that odors be transmitted 
in a current through the nostrils. The purpose of sniffing 
is to render the current stronger and the impression thereby 
more intense. 

The delicacy of the sense of smell is remarkable, it being 
possible to discern the presence of an odorous substance in 
quantities so minute as to be undiscovered by spectrum anal- 
ysis, T oo"o! o""oo~ o" °^ a g^i 11 of musk being distinctly smelled. 

The delicacy of the sense of smell varies greatly in dif- 
ferent individuals and different animals. As a rule, savage 
races possess this power to a higher degree than do the civ- 
ilized. It is highly developed in both carnivora and her- 
bivora. In the acuteness of this sense many animals surpass 
man, as is seen in the dog which is able to track the animal 
in the chase by scent, as well as to tell the track of his master. 



THE ORGAN OF SMELL. 383 

Subjective Sensation. — The friction of the electric ma- 
chine produces an odor like that of phosphorus. By Hitter 
it was observed that when a galvanic current was applied 
to the organ of smell, besides the impulse to sneeze and the 
tickling sensation excited by it in the filaments of the fifth 
nerve, a smell like that of ammonia was excited by the neg- 
ative pole and an acid odor by the positive. 

Frequently a person seems to smell something which is 
not present; this is especially true of nervous people, but it 
may happen to every one. 

Aside from being a source of pleasure, the sense of smell 
is protective. While the mouth sense of taste guards the gate- 
way to the alimentary tract from unpleasant and injurious 
substances, so the sense of smell guards the air passages from 
injurious gaseous substances. 



CHAPTER XVIIL 

VISION. 
EXPERIMENTS AND DEMONSTRATIONS. 

Dissection of the Eye. — Notice the position and relation 
of the eye in the subject (cat or rabbit) nsed. Examine the 
coverings of the eyes (eyelids). Notice the number and 
arrangement of the marginal hairs (eyelashes). Do they 
seem to have any definite arrangement ? Compare the outer 
appearance of the eye you are dissecting with that of the 
human eye. What difference do you note ? How do you 
account for the difference ? Lift the eyelid, and examine 
margin and under surface with a low power lens. Notice 
number of the openings near the margin of the lids and the 
parallel row of bead-like glands (Meibomian glands) (Fig. 
156). Determine if you can the nature of their secretion. 
If it is oily, can you think of its use ? Examine the lining 
of the eyelid; trace it over the ball of the eye. This is a 
mucous membrane, and is called the conjunctiva. Lift the 
lids, and examine the inner angle (inner canthus) for two 
minute openings (puncta lachrymalia) , one above and one 
below, and which open into separate canals, which join to 
form the lachrymal sac, which in turn opens below into the 
nasal duct. Examine the outer angle (outer canthus) near 
its upper border, for a gland (lachrymal gland). Determine 
if you can its opening ducts. This is the gland that secretes 
the chief fluid for the moistening of the conjunctiva. 

With the bone forceps or cartilage knife cut away part 
of the outer and upper part of the bone of the orbit. With 
scissors cut away the membrane that covers the front of the 
eyeball. Notice how it is reflected over the under surface 
of the eyelids. Do you see any difference in the part that 
384 



EXPERIMENTS. 385 

covers the eyeball from that which lines the lids? This will 
expose the surface of the eyeball. Look for seven muscles 
joined to the eyeball. 

Xotice: (1) the one which follows the roof of the orbit 
and is attached to the upper eyelid (levator palpebral supe- 
rioris), and which has its origin near the entrance of the 
optic nerve into the orbit; (2) the one which has its origin 
near the same place as the levator, takes an outward and 
oblique direction to the inner and upper part of the orbit, 
passes through a pulley, and then back to join to the eyeball 
at its nasal side (superior oblique muscle) (Fig. 157) ; what 
movement would its contraction give to the eyeball? (3) 
the muscle just below the one which moves forward and 
is joined to the upper part of the eyeball (superior rectus) ; 
(4) the muscle below the superior rectus, originating by 
two tendons passing forward and attached to the temporal 
side of the eyeball (external rectus) ; (5) the muscle hav- 
ing a similar origin, but on the opposite side of the optic 
nerve, passing forward and inward to join the nasal side 
of the eyeball (internal rectus) ; (6) the muscle passing 
downward and forward and inserted to the lower forepart 
of the eyeball (inferior rectus) ; (7) the muscle originating 
from the inner angle of the orbit passing forward and in- 
serted to the nasal side of the eyeball inward and below the 
external rectus. 

Xotice the entrance of the optic nerve. With the bone 
forceps cut away the bone, and trace the optic nerve as far 
as you can. Xotice the crossing (the chiasma). 

For the dissection of the eyeball it is best to use the eye 
of the ox or sheep, which may be obtained of the butcher. 

Hold the eyeball on the dissecting board with one hand, 
and with a pair of sharp scissors carefully make an incision 
through the cornea near the margin. With a pair of forceps 
gently raise the cut edge of the cornea so that the scissors 
may be inserted, and it may be cut around and removed 
without injuring the iris. Xotice the dark membrane (iris) 
which is thus exposed. Xotice the shape and size of the 
opening (pupil) in its center. With the forceps lift up the 
margin, and determine whether it is attached to the bodies 
beneath. Xotice the coloring and markings of the iris. 

Cut around the margin of the iris. Xotice the form and 
nature of the bodv (crystalline lens) now exposed. Make 

25 



386 VISION. 

a light gash across the surface of the lens ; cut through the 
outer coat (the capsule of the lens), which envelopes the 
lens. Gentle pressure with the thumb and finger on the side 
of the eye will cause the lens to be forced out. Place it on a 
clean piece of writing paper. Put it on a piece of newspaper, 
and examine the printing with it. Is there anything in its 
appearance to suggest its name? 

Make a drawing of the lens as it lies flatwise, and when 
lying edgewise. Compare the curve of the anterior and pos- 
terior surfaces. Enlarge the opening that has been made 
by cutting away the structure which covered the lens. On 
the inside of the strips thus removed there may be found 
radiating black ridges (the ciliary processes). Remove 
everything from the clear mass beneath (the vitreous 
humor). Notice its consistency. Notice the entrance of the 
optic nerve and the blood vessels, which may easily be seen 
through the transparent vitreous humor. 

If the light is not sufficient, view the specimen in stronger 
light. Now examine the tough outer coat (the sclerotic 
coat). Beneath this tough coat examine the dark coat (cho- 
roid coat). How does it compare in its supply of blood ves- 
sels with the other coats ? 

Examine the inner, nearly transparent, coat (retina). 
How do you account for its pinkish tint ? The color of the 
retina may be better seen by removing the vitreous humor. 
Determine if you can the relation of the retina to the nerve 
which enters the back of the eyeball (the optic nerve). 

Carefully remove the retina, making note of the layer 
and its consistency. The dark coat left on the layer beneath 
(the choroid) is the pigment layer of the retina which ad- 
heres to the choroid.- 

Turn the eye inside out, and carefully tear away the 
choroid coat, and notice how the blood vessels pass from one 
coat to the other. 

Experiments. — 1. Place two pins at each end of a shingle 
or thin board eight or ten inches long. Hold the board so 
that it will be about the distance used in reading, and so 
that the pins will be in line with the eye. Look closely at 



EXPERIMENTS. 387 

the first pin, and notice that the second is not clearly seen. 
Now look closely at the second, and notice that the first is 
not clearly seen. 

2. Hold the point of a pencil so that it will be in line 
with some object on the wall, as a picture. Look closely at 
the tip of the pencil, notice the picture becomes dim; now 
look closely at the picture which now becomes clear and the 
pencil dim. How shall we account for the changes noticed 
in the last two experiments ? 

3. Examine some object, as a lamp or vase, by means of 
a double convex lens (a reading glass), moving the lens 
forward or backward until you see the object inverted. With 
the lens unchanged in position, move the object forward. 
What effect has it upon the clearness of the image ? Now 
move the object until the image is clear again. How does 
your distance from the object compare with the first dis- 
tance ? Take the first position from which you' viewed the 
object, and view the object at its farthest distance by means 
of a double convex lens of greater curvature than the first. 
What is the effect ? Now view the object with a lens of 
smaller curvature than the one first used. Which gives you 
the clearer image ? 

Since it is not convenient for us to go to the objects in 
order to see them clearly, how could the parts of the eye 
be arranged so as to enable us to see distant objects without 
the trouble of going nearer to them? 

What would be the effect if the crystalline lens had the 
power of changing its curve ? To determine this, darken 
the room, and admit beams of light through two small holes 
about an inch in diameter. Put in their path lenses of dif- 
ferent degree of curvature. Xotice the effect. Which bends 
the rays most ? To focus distant objects, which must the 
crystalline lens be, of smaller or greater curvature than for 
near objects ? 

4. Place two small, black objects about two feet apart on 
a table covered with white paper. Close the left eye, and 
fix the right steadily on the left object, varying the dis- 
tance from the object. At a certain distance the right 
object will disappear. If the object be brought nearer or 
farther, then it will be plainly seen. This shows us that 
all parts of the retina are not equally sensitive to light. 
When the object disappears, the image falls on the part at 



388 VISION. 

which the optic nerve enters the eyeball. As this part is 
not sensitive to light, it is called the blind spot. 

5. Determine at what distance you can see the letters in 
Fig. 161. By normal eye these should be seen at twenty 
feet. Do you have to take them farther away or bring them 
nearer to see them ? 

6. Remove from the posterior part of an eyeball the 
sclerotic coat. Direct it upon some well-lighted object, and 
an inverted image will be seen on the retina through the 
thin choroid. Remove the lens; note the effect. Why is 
the image blurred or not apparent ? 

7. With a hand mirror reflect the sunlight on a white 
wall. Look at the spot for a minute or more, and then sud- 
denly remove the mirror. Notice a dark spot appears, the 
complementary color of white. 

8. Look steadily at a bright light. Turn away suddenly, 
or shut the eyes. Do you still see the light? Look steadily 
for a few seconds at a well-lighted window. Turn the eyes 
suddenly to a dark wall. Do you still see the window 
frames ? Notice the image on the wall is a negative one, 
the light parts being dark and the dark parts of the object 
light in the image. 

9. Rotate a stick slowly, and then increase the speed. 
Does the stick appear to make a continuous circle ? How 
do you account for what you see ? What properties of the 
retina do the three last experiments show ? 

How are what they call moving pictures made ? Upon 
what principle do we see continuous pictures ? 

10. Take a circular piece of cardboard, five or six inches 
in diameter. Paint on it alternate rings of different colors ; 
support by means of a pin so that the cardboard can be 
rotated. What kind of colors are the red and yellow ? What 
is the color you get by rapid rotation ? 

11. Draw lines as represented in Fig. .162. Can you see 
all the lines with the same clearness ? 

VISION". — TEXT. 

Appendages of the Eyes. — These are structures connected 
with the eye for its protection. The chief of these are the 
eyelids and the lachrymal apparatus. The eyelids are com- 
posed of a dense fibrous tissue (tarsal cartilage) covered ex- 



STRUCTURE OF THE EYE. 



389 



ternally by the skin and internally by a mucous membrane 
called the conjunctiva. Beneath the skin are the fibers of 
the orbicularis for closing the eyelids, and in the eyelid there 
is, in addition, the levator palpebrse for elevating the lid, 
and in the lower lid the depressor palpebrse to draw down 
the lower lids. 

On the inner margin of the eyelid may be seen the 
minute openings of a variety of sebaceous glands called the 




Fig. 157.— Lachrymal, Apparatus. 
1. Lachrymal gland. 2. Meibomian glands. _ The dots along edge of eyelid 



are the openings of the Meibomian glands. 
4. Canaliculus. 5. Nasal duct. 



3. Tear pore (puncta lachrymalia). 



Meibomian glands, as seen through the conjunctiva, contain- 
ing thirty rows on each side. Sometimes one or more of 
these become inflamed, producing what is called a sty. 

Along the free edges of the lids curved hairs, eyelashes, 
grow from large hair follicles to which sebaceous and mod- 
ified sweat glands are attached. 

After lining the eyelid, the conjunctiva is reflected over 
the front of the eyeball, becoming adherent to the sclerotic 
coat, its epithelial portion only passing over the cornea. The 
conjunctiva of the lids is thicker than the other portions, 
very vascular and sensitive, being freely supplied with nerve 



390 VISION. 

filaments, and has a number of mucous glands where reflec- 
tion begins. 

While the mucus aids in some degree in keeping the sur- 
face of the eye moist, the chief fluid for this purpose is the 
secretion from the lachrymal gland. This gland is situated 
(Fig. 157) in the upper and outer part of the bony orbit 
with its under surface resting on the eyeball. It is oval in 
shape and about the size of an almond. In structure it is 
a compound {racemose) gland consisting of several lobules, 
the acini, which are lined by cylindrical granular epithe- 
lium, being similar to that of a serous salivary gland. It 
opens by several ducts on the inner surface of the upper lid. 
Its watery secretion spreads over the eyeball, where its over- 
flow is usually prevented by the oily secretion of the Meibo- 
mian glands (Fig. 156) on the edge of the lids, and after 
passing over the surface of the eyeball, it collects in the inner 
angle (canthus) of the eye. Here it passes off by two small 
openings (puncta laclirymalia) , one above and one below, 
into two small canals (canaliculi) that unite to form a sac 
(lachrymal sac). This sac opens below into the nasal duct 
(Fig. 157), which runs in a groove of the superior maxillary 
bone and ends in the lower meatus of the nose. 

Like other secretions, it is under the control of a spe- 
cial center of the nervous system. Various sensory im- 
pulses, as pungent smells or irritating vapors, may produce 
reflex stimulation of this center, and lead to such a 
copious secretion that the liquid overflows as tears. Strong 
emotions, as great joy, or sorrow, may produce the same 
effect. 

The Eyeball.— The eyeball is nearly spherical in form, 
and consists of segments of two spheres of different sizes. 
The front portion, amounting to about one sixth of the eye- 
ball, is a segment of a small sphere; the posterior portion 
forming the rest of the eyeball is a segment of a larger sphere. 
It is composed of three layers, which inclose fluids and solid 
bodies called humors (Fig. 158). The investing coats are 
(1) the outer tunic, consisting of the sclerotic coat and cor- 



STRUCTURE OF THE EYE. 



391 



nea; (2) the middle tunic, made up of choroid, iris, and 
ciliary processes; (3) the inner tunic, retina, spread out 
over the inner and back portion of the choroid. The refract- 
ing media or humors are, in order from before backward, — 
the aqueous humor, the crystalline lens, and the vitreous 
hmnor. By the 
iris and crystal- 
line lens the in- 
terior of the eye 
is divided into 
two chambers, a 
small anterior 
eh a m b e r 
which contains 
the aqueous 
h u m o r , and 
a posterior 
chamber con- 
taining the vit- 
reous humor. 

Outer Tunic. 
— The sclerotic 

v m ° ' Fig. 158. — Coats of the Eyeball. 

158). This is l. Cornea. 2. Sinus venosus. 3. Conjunctiva. 4. Cili- 

, ary muscles. 5. Sclerotic. 6. Choroid. 7. Retina. 8. 

tlie Strong, Fovea centralis. 9. Optic nerve. 10. Iris. 11. Crystalline 

, n , lens. 

dense fibrous 

membrane which forms the posterior five sixths of the outer 
tunic of the eyeball. Its external surface is white (forming 
the white of the eye), and receives the insertion of the 
muscles of the eyeball (the recti and oblique muscles) ; its 
inner surface is brown, and connected by fine cellular tissue 
to the outer surface of the second coat It is composed of 
white fibrous tissue with some fine elastic fibers and numer- 
ous connective tissue corpuscles. Behind, a little to the inner 
or nasal side, it is pierced by the optic nerve, the fibrous 
sheath of the nerve becoming blended with that of the scle- 
rotic. Xear the entrance of the optic nerve it is also pierced 




392 VISION. 

by small arteries and nerves, the ciliary arteries and nerves, 
which are distributed to the sclerotic, choroid, and iris. The 
artery for the retina passes in through the middle of the optic 
nerve, its branches being distributed to the inner surface of 
the retina. 

Cornea. — This is the transparent circular membrane 
(Fig. IT) forming the fore part of the outer tunic, set, as 
it were, into the sclerotic, with which it is continuous all 
around. It consists of: A stratified layer of epithelial cells, 
derived from the conjunctiva and continuous with that layer 
of eyelids: an anterior elastic lamina beneath it, about one 
twenty-fifth of an inch thick, is made up of five layers. The 
cornea is covered by stratified epithelium, consisting of seven 
or eight layers of cells, the superficial one being flattened and 
scaly, and the deeper ones more or less columnar. Just below 
this is the anterior homogeneous lamina of Bowman, which 
differs from the general structure of the cornea in being more 
condensed. It is composed of an intercellular ground sub- 
stance of rather obscurely fibrillated flattened bundles of 
connective tissue, arranged parallel to the free surface, and 
forming the boundaries of branched anastomosing spaces in 
which the corneal corpuscles lie. These corpuscles have been 
seen to execute amoeboid movement. Limiting the posterior 
surface is the posterior homogeneous lamina {membrane of 
Descemet), which is elastic in its nature. The inner surface 
of the cornea (Fig. IT) is bounded by a single layer of cu- 
bical epithelial. 

The cornea is devoid of blood vessels, except a few capil- 
laries at its circumference. Its nutrition is effected by the 
passage of the lymph through branched spaces in which the 
corneal corpuscles lie. 

The nerves of the cornea are large and numerous, and 
are derived from the ciliary nerves. They traverse the sub- 
stance of the cornea in which some of them near the anterior 
surface break up into axis-cylinders, and their primitive 
fibrillse. The latter forms a plexus beneath the epithelium, 
from which delicate fibrils pass up between the cells, anasto- 



STRUCTURE OF THE EYE. 393 

mosing with horizontal brandies and forming an intraepi- 
thelial plexus. Most of the primitive fibrilke have a beaded 
appearance. This is what makes the conjunctiva so sensitive 
to particles of dust, etc. Running round the margin of the 
cornea in the sclerotic is a small lymphatic channel called 
the canal of Schlcmm. 

The Middle Tunic. — This is made up of the choroid, 
and, like the sclerotic, is found on the posterior five sixths of 
the eyeball. It is a highly vascular membrane, its blood ves- 
sels being derived from ciliary arteries and veins. The vas- 
cular network is held together by elastic connective tissue in 
which lie large stellate corpuscles and dark pigment. This 
pigment serves to assist in absorbing the light entering the 
eye and prevents absorption. 

Resting upon a fine elastic layer {membrane of Bruch) is 
a denser layer of blood vessels, which serve' to nourish the 
underlying pigment layer of the retina. 

The choroid coat ends in front in seventy or eighty merid- 
ionally arranged radiating plates (ciliary processes), which 
consist of blood vessels, fibrous connective tissue, and pig- 
ment corpuscles. They are lined by a continuation of the 
membrane of Bruch. The ciliary processes end abruptly 
at the margin of the crystalline lens. 

From the junction of the cornea and sclerotic arises the 
ciliary muscle. This is a ring of muscle 3 mm. broad and 
8 mm. thick, made up of fibers running in three directions: 
(1) Meridional fibers near the sclerotic; (2) fibers passing 
to be inserted into the choroid behind the oiliary processes; 
and (3) more internal circular fibers, forming a sphincter 
muscle (muscle of Mutter). 

The ciliary muscles thus form a ring around the eye 
between the sclerotic and ciliary processes, and their contrac- 
tion draws the choroid forward, and thus relaxes the sus- 
pensory ligaments of the crystalline lens, making the lens 
more convex, and aiding, as we shall see, in the accommoda- 
tion (Fig. 163) of the eye. 

The continuation of the choroid inward bevond the cil- 



394 VISION. 

iary processes forms the iris. It is a fibro-muscular mem- 
brane, perforated by a central aperture, the pupil. It is 
composed chiefly of blood vessels and connective tissue with 
pigment and unstriated muscle. On its posterior surface 
is a pigment layer derived from the retina. 

The iris proper is made up in front of connective tissue 
with corpuscles which may or may not contain pigment, 
and, behind, of a similar tissue, supporting blood vessels in- 
closed in connective tissue. This part of the pigment cells 
is usually well developed, as also are many nerve fibers radi- 
ating toward the pupil. Surrounding the pupil is a layer 
of circular unstriped muscle, the sphincter pupillce. In some 
animals there are also muscle fibers which radiate from the 
sphincter into the substance of the iris, forming the dilator 
pupillge. Anteriorly the iris is covered by a layer of epi- 
thelium continued upon it from the posterior surface of the 
cornea. 

Retina. — -The retina (Fig. 159) is a delicate semitrans- 
parent membrane forming the inner, or third, tunic of the 
eyeball. It conforms in its curvature to the inner surface 
of the eye, being directed forward and apparently ending 
in front near the outer part of the ciliary processes in a 
finely notched edge (ora serrata), but really present to the 
very edge of the pupil. When fresh, it is semitransparent, 
slightly pinkish in tint, due to its blood vessels, but it becomes 
clouded and opaque on standing. It is from the expansion 
of the optic nerve, of whose fibers, with nerve cells, it is 
essentially composed. In the exact center of the retina is 
to be seen a round yellowish spot (macula lutea or yellow 
spot of Sommerring), about one twenty-fourth of an inch 
in diameter, and having in its center a small depression 
(fovea centralis). The optic nerve enters about one tenth 
of an inch in the inner part of the yellow spot. 

As the optic nerve passes forward from the ventral surface 
of the cerebrum to the orbit, it is invested by prolongations of 
the dura mater, arachnoid, and pia mater. At the entrance 
of the nerve into the eyeball the external sheath becomes 



STRUCTURE OF THE ftETINA. 



395 



continuous with the sclerotic, which at this part (lamina 
cribrosa) is perforated with holes to allow the passage of 
the optic nerve fibers and the pia mater with the choroid. 
At this point the pia mater becomes incomplete, and the 
subarachnoid and the superaraclmoid spaces become con- 
tinuous. From the pia mater is given off processes to sup- 




Fig. 159 A. —Diagram of the Elementary Structure of the Retina. 

1. Pigment cells. 2. Filaments of pigment cells. 3. Rod. 4. Body of rod 
cells. 5. Cone cells. 6. Filament of cone cell. 7. Bipolar cell. 8. Ganglionic 
cells ramifying in the various strata of the internal molecular layer. 9. Large 
canglionic cells joining with the inferior arborescence of the bipolar cells. 10. 
Fibers of optic nerve. 11. Horizontal cells. 13, 14, 15, 16. Many-formed cells 
of the inner reticular or molecular layer. 17. Centrifugal nerve "fiber. 18. Neu- 
roglia cells. 19. Epithelial cell (Miiller cell). 

port the nerve fibers. The nerve fibers are very fine, with- 
out their ordinary external nerve sheath, but having a little 
delicate myelin sheath : but as they pass into the retina, they 
lose their myelin sheath, and proceed as axis-cylinders. The 
nerve fibers of the optic nerve trunk are supported by neu- 
roglia. In the center of the optic nerve is a small arterv 
(arteria centralis retina?). 



396 



VISION. 



The number of fibers in the optic nerve has been esti- 
mated to be over 500,000. 

The retina 1 consists of nervous ele- 
ments arranged in several layers and 
supported by a delicate connective 
tissue. These elements may be divided 
into two kinds: (1) the supporting con- 
nective tissue (sustentacula!") (Fig. 
159) and (2) the nervous (Fig. 159). 

Structure of the Retina in Different 
Parts. — Toward the yellow spot all the 
layers of the retina become greatly 
thinned out, and almost disappear, ex- 
cept the rod and cone layers, which in- 
crease in thickness, but at the fovea 
centralis consist almost entirely of 
cones and cone fibers. Toward the edge 
of the yellow spot all the layers are 
present, but the ganglion layer in- 
creases in prominence, being made up 
of many layers of cells. At the optic 
pore, where the optic nerve enters the 
eye, only fibers are present, and as this 
part is insensitive to light, it is called 
the blind spot. 

At the ora serrata of the nerve 
fibers, ganglion cells and rods have dis- 




Fia. 159. B.— Layers of 
the Eetina. 
1. Pigment layer. 2- 
Layer of rods and cones. 
3. External limiting lay- 
er. 4. External molec- 
ular layer. 5. Spaces for 
the nervous elements 
and fibrous layer. 6. Ex- 
ternal granular layer. 
7. External nuclear lay- . v 

er. 8. internal granular appeared, and over the ciliary process 

or molecular layer. 10. 
Fibers of the < 
11. Internal 
membrane. 



r layer. 10. . .-, -i • 

optic nerve, the retina proper ceases, there being 
only the layer of cells known as the 
pars ciliaris retina?. 



Hn a vertical section, the following ten layers, naming from within outward, 
are usually distinguished — 

1. A Delicate Membrane (Membrana Limitans Interna) (Fig. 159).— This is in 
contact with the vitreous humor. This seems to bear the same relation to the 
retina as the neuroglia does to the nerve tissue, that of a supporting character. 
This may be seen by a study of Fig. 159. 

2. Optic Nerve Fiber.— This is a layer varying greatly in thickness in different 
parts of the retina. It consists of non-medullated fibers which interlace, some of 
which are continuous with the processes of the nerve cells which make up the 



LAYERS OF THE RETINA. 397 

The Chambers of the Eye. — The space behind the cornea 
and in front of the crystalline lens is called the anterior cham- 
ber. It is filled with the aqueous humor. The portion back 

next layers. The fibers are supported by the connective tissue (sustentacular 
fibers). The nerve fibers become less numerous anteriorly, and end at the ora 
serrata. 

3. Layer Ganglionic Corpuscles. — This layer consists of large multipolar 
nerve cells having prominent nuclei. In the yellow spot this layer is very thick, 
being made up of several layers. The cells are imbedded in the spaces of 
the connective tissue network, and so arranged as to have their axis-cylinder 
processes inward, being continuous with the layer of the optic nerve fibers. 
Above, the cells become much branched. 

4. Inner Molecular Layer. — This layer is fine, granular in appearance. It is 
made up of a fungiform connective tissue traversed by numerous, very fine 
fibrillar processes of the nerve cells and the minute branches of the processes of 
the nuclear cells of the layer above. 

5. Inner Nuclear Layer. — This is composed chiefly of small, round cells, which 
consist of a small amount of protoplasm and a large ovoid nucleus, most bipolar, 
giving off one process outward and another inward. The cells vary much, 
resemble the ganglion corpuscles of the cerebellum, and are of three kinds. 

G. Outer Molecular Layer. — In structure and appearance it closely resembles 
the inner molecular layer, but it is much thicker. It is made up of finely dotted 
connective tissue and nerve fibrils of the branchings of the rod and cone fibers 
above, and of the inner cells below. 

7. Exta-nal Nu clear Layer. — This layer is made up of small cells resembling 
those of the internal granular layer; they have been classed as rod and cone 
fibers, accordingly as they are connected with the rods and cones respectively. 
They are lodged in the meshes of the connective tissue framework. 

8. Memhrana Lirnitans Externa. — This is a delicate, well-defined membrane, 
which clearly marks the internal limit of the rod and cone layer, being made up 
by the junction of the bases of the sustentacular fibers, externally. The rods 
and cones are supported by small hair-like processes which project outward 
between them. 

9. Layer of Rods and Cones. — This is probably the most important layer of the 
retina. It is thought to be directly or indirectly continuous with the nervous 
layer proper. The bodies of which it is composed are arranged at right angles 
to the external lirnitans membrane and are similar in general form but vary in 
certain details, and are supported by the hair- like processes from the external 
lirnitans membrane. 

The Rods. — Each rod is made up of two parts which differ very much in 
structure, and are known as the outer and inner limbs. The outer limb of the 
rod is transparent, doubly refractive, about 30^ long 2 fi broad. It is said to 
be made up of fine superimposed disks. It resembles in some ways the myelin 
sheath of a medullated nerve. It swells on exposure to light, and is part of the 
layer in which the pigment called visual purple is found. The inner limb is 
longitudinally striated at its outer part and granular at its inner part; it has 
about the same length as the outer limb, but is broader. Each rod is connected 
internally with the rod fiber, the internal end of the rod fiber terminating in 
minute branches in the internuclear layer. 

The Coxes. — Like the rods each cone is made up of two limbs. The outer 
limb is tapering, about one third the length of the corresponding part of the rod, 
and similar to it in structure. There is no visual purple found in the cone. 
The inner limb of the cone is broader in the center. Each cone is connected by 
its internal end with a cone fiber which has a structure similar to that of tbe rod 
fiber, but is much stouter, and with its nucleus nearer tLe external lirnitans 
membrane. The tunic portion of the inner end is like that of the outer. In tbe 
retina of man the rods are far more numerous, except in the fovea centralis 
where only the cones are present, and also in the anterior part of the retina 



398 VISION. 

of the crystalline lens and bounded by the retina is called the 
posterior chamber. It contains the vitreous humor. 

Humors of the Eye. — These are the aqueous humor, the 
crystalline lens, and the vitreous humor. As has been stated, 
the aqueous humor is contained in the anterior chamber of 
the eye. It is essentially a diluted lymph with a small 
amount of proteid material. It contains salts, the chief of 
which is sodium chloride, sometimes a substance which re- 
duces copper sulphate ; but it is not sugar, and has traces of 
urea and sarcolactic acid. By some it is thought that the 
aqueous humor is secreted by glands in the ciliary region, 
but the cavity itself is without doubt a lymph sac. 

The Crystalline Lens. — This is situated behind the iris, 
being supported in place by the suspensory ligaments fused 
to the anterior surface of the capsule. The suspensory liga- 
ment is derived from the membrane {hyaloid) which incloses 
the vitreous humor. It is biconvex, having its posterior sur- 
face of greater curvature than its anterior. It consists of a 
capsule and lens. The capsule is a transparent, elastic mem- 
brane, and strongest in front. The lens consists of a num- 
ber of concentric laminae which, after hardening, may be 
peeled off like coats of an onion, each lamina consisting of 
ribbon-like fibers with serrated edges. The inner laminae are 
closely applied, and form a dense core, or nucleus. The 
fibers which are developed by the elongation of cells run 



near the or a serrata. It has been estimated that there are about three million 
cones in the retina of man. In most birds, cones usually predominate in number, 
but in nocturnal birds and some nocturnal animals, as the bat, hedgehog, mouse, 
and mole, only rods are present. 

10. Pigment Cell Layer. — This layer was formerly considered as a part of the 
choroid. It consists of cells which cover and entirely surround the outer limbs 
of the rods and cones. This is a single stratum of hexagonal epithelial cells, 
containing black pigment. They are present in all parts of the retina except at 
the entrance of the optic nerve. The outer part of the cell is smooth and flat, 
but the inner part is prolonged, on exposure to light, into fine processes that 
extend between the rods. The pigment granules lie in the inner part of the cell, 
and after exposure to light extend along the prolonged cell processes, where by 
their agency, the visual purple of the retina becomes developed in the outer 
part of the rods. There is no pigment in the cones. Visual purple is bleached 
by exposure to light, and the function of the pigment cells appears to be to 
restore the purple coloring matter after being bleached by light. Light causes 
the processes of the pigment cells to extend inward between the rods, while 
darkness causes the processes to retract. 



VITREOUS HUMOR. 399 

from front to back, being so arranged that no fibers from 
one pole of the lens go to the other (Fig. 158). The lens con- 
tains no blood vessels, its nutrition being effected by the 
blood vessels of the choroid. 

Vitreous Kumor. — The vitreous humor occupies the 
posterior chamber of the eye. It consists of a semifluid sub- 
stance contained in the meshes of an indistinct connective 
tissue. It is inclosed by a distinct membrane (membrana 
h yah idea) from the anterior surface of which, at the ora 
serrata, fibers pass off to the back of the lens capsule, form- 
ing an incomplete canal (canal of Petit). Fibers also pass 
forward over the ciliary processes to be attached to the cap- 
sule of the front surface of the lens to form the suspensory 
ligament (zonule of Zinn). It contains water, with a little 
over one per cent of proteid matter and salt The fluid 
appears to belong to the same system as the aqueous humor, 
there being a communication through the suspensory liga- 
ments. As it has no blood vessels in the adult, it must derive 
its nutrition from the surrounding vascular structures. 
There is a small canal passing from the back forward 
and terminating at the capsule of the lens. This canal 
(canal of Stilling) takes the place of an artery which exists 
in the foetus. 

Blood Vessels of the Eye.— The eye is richly supplied 
with blood vessels. Supplying the eyelids and glands are 
the palpebral and lachrymal branches, and the conjunctival 
branches which pass also to the edges of the cornea. The 
coats, or tunics, of the eyeball are supplied by two distinct 
sets of vessels: (1) the vessels of the sclerotic, choroid, and 
iris, and (2) the vessels of the retina. The former are the 
short and long posterior and anterior ciliary arteries. The 
short posterior ciliary arteries enter the first part of the scle- 
rotic around the optic nerve (Fig. 160), and are distributed 
to the choroid and ciliary processes. The long posterior 
ciliary arteries enter the choroid behind, and passing forward, 
are distributed to the ciliary muscles and to the iris, and 
with the anterior ciliary, which enters near the insertion of 



400 VISION. 

the recti muscles, form by their anastomosis the rich choroidal 
plexus. They also supply the iris and ciliary processes, and 
form a very highly vascular circle around the outer margin 
of the iris and adjoining portion of the sclerotic. 

The bloodshot eye is due to congestion of the conjunctival 
vessels, while the pink zone sometimes surrounding the 
cornea indicates deep-seated ciliary congestion, and the dis- 
tinctness of the two sets of vessels may be thus indicated. 
From the capillaries numerous veins arise, which form a 
vorticose arrangement 6n the surface of the choroid, and 
unite for the most part into four large trunks that pass out 
of the choroid about midway between the cornea and the 
optic nerve. 

The retina is supplied by branches from the arteria cen- 
tralis retinae, which enters the eyeball along the center of the 
optic nerve. It gives off branches which ramify all over 
the retina, but chiefly in its inner layers. The capillaries 
unite to form a central canal. Except near the entrance of 
the optic nerve the two sets of blood vessels of the eyeball are 
quite distinct. 

Nerves of the Eye. — The optic nerves are the special 
nerves of vision. Passing backward from the retina, the two 
optic nerves meet, ventral to the floor of the third ventricle, 
and cross each other, forming the optic chiasma ; they then 
continue under the name of optic tract. In the chiasma the 
decussation of fibers takes place. In man the fibers which 
belong to the temporal half of the eye, in which the nerve 
ends, pass into the optic tract ; i. e., of the same side, while 
the fibers which belong to the nasal half pass into another 
tract, the optic tract of the opposite side. Thus the fibers 
of the temporal half of the right eye and the nasal half of 
the left eye pass into the right optic tract, and the fibers of 
the temporal half of the left eye and the nasal half of the 
right eye pass into the left optic tract. It will be noticed 
from this that the temporal half of one eye corresponds to 
the nasal half of the opposite eye, and that each optic tract 
contains fibers from half of each eye. The degree to which 



NERVES OF THE EYE. 



401 



the decussation takes place varies in the different types of 
animals, the difference having reference to the amount of 
binocular vision, and this in turn having relation to the posi- 
tion of the eye and the prominence of the facial features; 
e. g., in fish, with laterally placed eyes, binocular vision is 
not possible, so that the decussation of the fibers is complete. 

The chiasma also contains in its hinder part fibers which 
have no connection with the optic nerves or the eyes; they 
are simply commissural tracts passing from one side of the 
brain, from the median corpus geniculatum along one optic 
tract through the chiasma to the other optic tract and to the 
median corpus geniculatum of the other side of the brain. 

Each optic tract crosses obliquely, being in crossing firmly 
attached to the ventral surface of the cms cerebri of the same 
side, and is soon lost to view, being covered by the temporo- 
sphenoidal lobe of the cerebrum. By removing this lobe, 
the optic tract is brought to view, and is seen to sweep dor- 
sally around the crus toward the dorsal side to become con- 
nected with the two (lateral and median) corpora geniculata 
(Fig. 62). The fibers which come from the median corpora 
probably have no concern with vision, but are, as has been 
stated, simply commissural. The fibers concerned with 
vision end in three main ways : ( 1 ) those in the lateral corpus 
geniculatum; (2) a very large number of fibers pass the 
corpus geniculatum on its ventral and lateral surface spread 
out into the pulvinar; (3) those which take a more median 
direction pass to the corpus quadrigeminum. It is probable 
that all of these centers are concerned with vision. While 
the areas mentioned are the chief endings of the optic nerves 
and the three primary visual centers, there are good reasons 
for believing that some of the fibers of the optic tract pass 
by the crus cerebri straight to certain parts of the cerebral 
hemisphere, although their endings have not been made out. 
The trophic center of the optic nerve is in certain cells of 
the retina, as is shown by section of the optic nerve on re- 
moval of the eye of an adult animal, which leads to degenera- 
tion in the optic nerve and optic tract 
2G 



402 VISION. 

In addition to the optic nerve, other nerves enter the 
eyeball. The ciliary nerves pierce the sclerotic around the 
optic nerve. These are mainly branches of the first, or 
ophthalmic, division of the fifth cranial. Accompanying 
them are branches from the sympathetic system. After pass- 
ing through the sclerotic the ciliary nerves run forward be- 
tween it and the choroid, and are distributed to the iris and 
ciliary muscles. There are- twigs from the first branch of 
the fifth nerve which supply the cornea; fine fibrils passing 
between the epithelial cells to the conjunctival layer giving 
to it its acute sensibility to foreign particles. Disease or 
injury of this branch of the fifth nerve destroys the sensibil- 
ity of the surface of the eyeball. The vasomotor fibers to 
the blood vessels are included in the ciliary nerves. 

The chief motor nerves of the eye are the third pair of 
cranial nerves (motores oculi). Each motor oculi supplies 
all the muscles of the eye except the superior oblique and 
external rectus ; it also sends filaments to the elevator of the 
eyelid and to the iris and ciliary. In addition to controlling 
the movement of the eyeball, this nerve regulates the amount 
of light entering the pupil, and brings about accommodation. 
A bright light acting through the retina and optic nerves 
stimulates the center of origin of this nerve, exciting reflexly 
the pupil to contraction. 

The fourth pair of cranial nerves (troclilearis) sup- 
plies the superior oblique muscle of the eye. The sixth pair 
of cranial nerves (abducentes) supplies the external rectus 
muscle. 

Muscles of the Eye. — The upper lid is raised by the 
levator palpebral superioris; the orbicularis palpebral close 
the eyelids. There are six muscles (Fig. 161) which are 
concerned with the movements of the eyeball, four straight 
muscles (recti) and two oblique. The four recti arise behind 
it by a continuous tendon at the bottom of the orbit, and pass 
forward, one above (superior rectus) and one below (inferior 
rectus). One on the outer side (external rectus) and one on 
the nasal side (internal rectus) are inserted by short mem- 



MUSCLES OF THE EYE. 



403 



branous tendons into the fore part of the sclerotic coat. 
The superior oblique arises from the bottom of the orbit, and 
passing forward, terminates in a tendon that passes through 
a cartilaginous ring or pulley, attached to the frontal bone, 
after which the tendon 
is reflected backward 
and downward to be in- 
serted into the upper 
part of the sclerotic 
coat, midway between 
the cornea and the en- 
trance of the optic 
nerve' The inferior 
oblique muscle arises 
at the lower and front 
portion of the orbit, 
passes backward a n d 
upward, e n d i n g in a 
tendinous expansion in- 

cprfprl nnrlpr t1tp p^r+pv- "oris. 2. Obliquus superior. 3." Fibro-cartilage 
beneu unuer me exier ring or pu u ey of the obliquus superior. 4. 

nnl rpH"i-i<? nt tliP rmfpr Re .£tus superior muscle. 5. Rectus inferior 
LLdl lecillb db me Oilier 6 Rectus externus. 7. Ligament of Zinn 




Fig. 161. 



Muscles of the Ete. 

1. Levator palpebras supe- 



and 



and 

nnctflTlAi- t-.qi>+ n-P origin of the lower head of rectus externus. 8. 

pObieilOl pan OI Upper head of rectus externus. 9. Internal for 

,i in passage of the motor oculi and abducens 

me eve ball. nerves. 10. Obliquus inferior. 11. Optic nerve 

mi , c 12. Sphenoid sinus. 13. Nasal orifice. 

1 lie movements 01 
the eye may be learned by a study of the table below : — 



MOVEMENTS OF THE EYE. 



Direction of Movement. 
Inward. 
Outward. 
Upward. 
Downward. 
Upward and downward. 

Inward and downward. 

Outward and upward. 

Outward and downward. 



By What Muscles Accomplished. 

Internal rectus. 

External rectus. 

Superior rectus, inferior oblique. 

Inferior rectus, superior oblique. 

Internal and superior rectus, in- 
ferior oblique. 

Internal and inferior rectus, su- 
perior oblique. 

External and superior rectus, 
inferior oblique. 

External and inferior rectus, 
superior oblique. 



404 VISION. 

THE OPTICAL APPARATUS. 

For convenience of description we may consider the 
optical apparatus of the eye (Fig. 158) as made up of (1) 
a system of transparent refracting 1 surfaces and media by 
means of which images of external objects are formed on 
the retina; (2) a sensitive screen, the retina, capable of 
being stimulated by luminous objects and of sending through 
the optic nerve such impressions as to produce in the brain 
visual sensations; (3) an apparatus to turn the eyes in the 
same direction, making possible binocular vision; (4) an 
apparatus for focusing objects at different distances (accom- 
modation) ; (5) means by which the amount of light received, 
on the retina may be regulated. As an optical instrument 
the eye may be compared to a photographic camera. 

" The refracting media and surfaces of the eye are the 
anterior surface of the cornea, the posterior surface of the 
cornea, the aqueous humor, the anterior surface of the crys- 



iln order that we may better understand the working of the eye in the forma- 
tion of an image, let us briefly consider a few of the principles of optics by 
which images are formed. A single line of light is called a ray. A substance 
which permits the passage of light through it is called a medium. Media differ 
greatly in their power to transmit light, and thereby very materially affect the 
direction and velocity of the light which passes through them. When the ray 
strikes the medium at right angles, the principal effect is to decrease the 
velocity of the light; but when it strikes the surface obliquely, or the surface of 
the medium is curved, it changes the direction of the ray on entering the new 
medium, and thus bending (refracting) from its course is governed by the law that 
the ray in passing from a rarer to a denser medium, is bent toward the perpen- 
dicular to the plane of refraction; and if from a denser to a rarer medium, it is 
bent from the perpendicular. The angle which the incident ray (the one from 
the source of light) makes with the perpendicular of the refracting medium, as 
compared with the angle made by the refracted ray extending perpendicularly, is 
called the index of refraction, and is generally expressed by the ratio of sines of 
their angles. 

When a ray of light enters a, medium, it may be (1) bent from its course 
(reflected) (Fig. 163) by the resistance, of the medium; (2) on entering the medium, 
by its resistance it may be converted into heat (absorbed), and (3) it may pass 
through the medium, but be changed in its direction (reflected). 

A lens is a transparent medium bounded by at least one curved surface. 
When the lens has one convex surface and one plane surface, it is called piano, 
convex; and when having two convex surfaces, double convex. To which of 
these does the cornea with the aqueous humor, with the iris and the crystalline 
lens, correspond ? 



ACCOMMODATION IN VISION. 405 

talline lens, the substance of the lens, the posterior surface 
of the lens, and the vitreous humor. 

From this it will be seen that there are five surfaces, 
and, including the air, five media. This would at first 
thought seem to make the refracting system very compli- 
cated, but for all practical purposes it may be reduced to a 
much simpler form — the cornea with its surfaces as one 
medium, the aqueous and vitreous humors as another, and 
the crystalline lens and its surface as another. 

A careful study of Fig. 163 will make clear how the 
image is formed on the retina. Trace the pencil of rays 
represented by the diverging lines, and determine, if you 
can, why the image on the retina is inverted and smaller. 

Determine from Diagram 163 the effect of shortening 
or lengthening the eyeball. From our experiments we have 
learned that the focus of rays is partially dependent upon 
the distance of the object from the lens. If then the retina 
of the eye should be in focus for a near object, it would be 
out of focus for distant objects. 

The power to adapt the eye to see near and far objects 
is called accommodation. This power resides primarily in 
the crystalline lens, by its power to increase or decrease the 
convexity of its anterior surface, and thus change the focus. 
Study Fig. 163. Should the convexity be increased or 
decreased for viewing near objects when the eye is focused 
for a distant object ? The amount of change for an object 
at a great distance and for one at the distance of four inches 
is only .143 of an inch. 

The crystalline lens having no inherent power of con- 
traction, changes in its form must be produced by power 
from without; this power is given by the ciliary muscles 
(tensor choroidal). By its contraction the ciliary muscle 
draws forward the ciliary processes to which the capsule of 
the lens is attached; in this way the tension of the capsule 
is decreased, allowing the lens to become more convex. On 
the diminution or cessation of the action of the ciliary mus- 



406 



VISION. 





AstickaticFan 





B 



V Z B 



D F 

c 



H KO S 



Fig. 162. 



SSSSSSS 
E 



A. Irradiation. 

B. Astigmatism. 

C. Test type. Should be easily read by a normal eye at ten feet. 

D. Test for the " Blind Spot." 

E. Defective visual judgment. Look at object inverted. 



FIELD OF VISION. 407 

cle the lens returns to its former shape by virtue of the elas- 
ticity of the ciliary processes. The eye is usually focused for 
distant objects, so the adjustments have to be made prin- 
cipally for near objects. There is a limit to the power of 
accommodation. This can be shown by bringing a book 
nearer and nearer to the eye, the words at last becoming in- 
distinct from the lack of power of the lens to accommodate 
to the distance, and bring the light to a focus on the retina. 

During accommodation there are two other marked 
changes which take place in the eyes: (1) the eyes con- 
verge by the action muscles of the eyeball (see table, page 
403) ; (2) the pupils contract. Xote that the contraction 
of all the muscles which are concerned with accommodation 
— viz., the ciliary muscles, the recti muscles, and the sphinc- 
ter pupilke — are under the control of the third nerve, but 
should the superior oblique be concerned in the movement 
of the eyeball, the fourth nerve is also concerned. 

The limit of accommodation in the normal eye, for the 
near point, is four inches; for the remote point, an infinite 
distance. Owing to the lens becoming less elastic and the 
ciliary muscles weaker, the near point gets farther away as 
age advances. This defect in old people is called long-sight 
(presbyopia), due to the changed form of the eyeball. 

Field of Vision. — By the visual field is meant that por- 
tion of the external world visible at one time. We can in- 
crease the field of vision by the movements of the eyes and 
those of the head. We generally use both eyes in looking 
at an object, and our normal vision is binocular. By a study 
of Fig. 163 it will be seen that the visual field of the left 
eye differs from that of the right eye. Xot only is the 
image on the retina inverted, but also the position of the 
eye is changed; i. e., the left-hand side of the retinal image 
corresponds to the right-hand side of the visual field, and 
the right-hand side of the retina image corresponds to the 
left-hand side of the visual field. It will also be seen that in 
the right eye the right-hand side of the visual field corre- 
sponds to the nasal half (that part of the retina lying on the 



408 



VISION. 



side of the axis of the eye nearest the nose) of the retina, 
and the left-hand side of the visual field, to the temporal 
half (that part of the retina on the temporal side of the axis 
of the eye) of the retina ; and in the left eye the right side 
of the visual field corresponds to the temporal half of the 




\ JR 




Fig. 163. —Optics op Vision. 

I. How the Image Is Formed on the Retina. 

AB. Object. A'B'. Image of object. AM. Incident ray from A. MN. Re- 
fracted ray in lens. NA'. Refracted ray to retina. AOA'. Secondary axis focus- 
ing with AMNA' at A'. Notice how these lines cause the inversion of the image. 
F. Principal focus. O. Optical center of crystalline lens. S'A'TP. Form of the 
eye in normal vision (emmetropic eye). Notice the image is brought to a focus on 
the retina. S'DTP. Form of the eyeball in a long-sighted eye (hypermetropic eye). 
Notice the eyeball is too short, and the image is brought to a focus back of the 
retina. S'CTP. Form of the eyeball in a short-sighted eye (myopic eye). Notice 
the eyeball is too long and the rays come to a focus in front of the retina. 

II. Visual Angle. 

The objects at the points BDF and M respectively are of the same height, but 
that the angle formed by the lines that come from their extremities to the point 
E decreases with the distance; i. e., the visual angle decreases with the distance. 

III. Accommodation. 

If any eye is in focus for the rays NE and ME (Fig. II) from the extremities 
MN, it would not be in focus for the rays AE and BE from the extremities of 
the object AB. Notice the lens in the last case is more curved and thicker. 
3. Capsule of crystalline lens. 4. Suspensory ligament. 5. Iris. 6. Ciliary proc- 
esses. 7. Ciliary muscles- 8, Selerotic coat. U. Cornea, 10, Canal of Schlemm. 



FIELD OF VISION. 



409 



retina, and the left side to the nasal half of the retina. 
From a study of Fig. 163 it will be seen that if an object 
is brought too close to the eye, it will be seen by one eye 
only, and hence the vision is monocular, and in this case 
restricted to the nasal side. It will be noticed that the field 
of vision is greater for the two eyes than it would be for 
one, as a portion of the field is common to both. 

In most cases the images of the objects looked at are 
small enough to be received by the corresponding points of 
the two fovea?, thus making the vision distinct, while those 
received outside of the fovea? are less distinct. Images not 
falling on the corresponding points, or imperfectly focused 
images, are not noticed, or at most, make a very weak im- 
pression on the brain. 

Movements of the Iris. — The iris performs in the eye a 
function similar to that of the diaphragm of a camera, by 




Fig. 163.— Continued 



IV. Diagram to Illustrate the Principle of Accommodation. 

A. Lens which focuses parallel rays at 3. 1, 2, 3. Course of a parallel ray from 
a distant, object. C. A near object. C5. An incident ray. If the object is to 
be seen clearly, the rays from it must be focused at 3. To do this the rays before 
reaching the lens A must be made parallel. This is accomplished by the lens 
B and as they come at so different angle. We could not see the object AB as 
distinctly as that of MN if the refracting apparatus of the eye was unchange- 
able, unless we moved toward the object until the visual angle AEB was 
equal to that of NEM. If, however, we had some way by which tho rays from A 
and B could be more refracted, they might be focused on the retina, and we could 
see them clearly from the point E. This is accomplished by changing the curva- 
ture and thickness of the crystalline lens. 1. Form of crystalline lens in view- 
ing object far away. 2. Form of crystalline lens in viewing near object in the eye 
by the thickness of the crystalline lens, which secures the same result by more 
highly refracting the incident ray. 

V. Binocular Vision. 

R. Right eye. L. Left eye. 0. Object. 1'. Axis of left eye. O 2\ Axis of 
right eye. C. Crystalline lens of right eye. A. Crystalline lens of right eye. 
COA. Optical angle. N. Ridge of the nose. 4 4'. Ray from anterior right 
corner. 3 3'. Ray from anterior left corner. Notice that each of these rays go 
to the nasal side of the axis of the eye. 5 C 5'. Ray from posterior left corner. 
6 A 6'. Ray from posterior right corner. Notice that the posterior rays also to 
nasal side of the eye. 5 A 5'. Ray from anterior left corner to right eye. 6 C &. 
Ray from anterior right corner to the left eye. Notice that in the last two cases 
the rays go to the ear side (auricular) of the eye; also that the impressions made 
on the left eye differ from those made on the right eye, and that by combining 
these impressions we get the proper notion of the object and its perspective. 



410 VISION. 

its contraction and relaxation increasing or decreasing the 
size of the pupil. As no light enters the eye except through 
the pupil, it serves to regulate the amount of light entering 
the eye. It also aids in correcting spherical aberration, and 
gives depth of focus. 

Among the causes which produce the constriction of the 
pupil, are: (1) an increased intensity of light; the greater 
the intensity, the greater the constriction; (2) the viewing 
of near objects in order to give clearness by cutting off the 
widely divergent rays that could not be focused at the same 
point as the less divergent; (3) the turning inward of the 
eyes, as looking at a near object with both eyes; (4) the 
action of such drugs as opium, administered internally, or 
aconite; early stages of chloroform and alcoholic poisons; 
and the local application of eserin ; (5) the division of the 
cervical sympathetic, or the stimulation of the third nerve; 
(6) sleep. 

Dilation 'of the pupil is produced ( 1 ) by lessening the 
intensity of the light: (2) by looking at distant objects; (3) 
by an excess of aqueous humor, in difficult breathing (dys- 
pnoea ) , or violent muscular effort, as in lifting heavy loads ; 
(4) by the local application of atropine and its allied alka- 
loid, or by the internal administration of atropine and its 
allies; (5) in the last stages of chloroform and opium poi- 
soning; (6) by paralysis of the third nerve; (7) by stim- 
ulation of the cervical sympathetic nerve. 

BINOCULAR VISION. 

Binocular Vision. — A single object forms an image on 
each retina, but ^ye see but one object under normal condi- 
tions. By pressing the eyeball out of its usual shape, one 
object may appear as two. It appears that certain parts of 
each retina are so related to each other that when an image 
of an object falls on these at the same time the two sets of 
sensations excited in the two parts are blended into one. 
Such parts are called corresponding, or identical, parts, and 
the conditions of single vision with two eyes are that the 



BINOCULAR VISION. 411 

images from the various parts of the object fall upon the 
corresponding parts of the retina. 

The spheres of the two retina? may be considered as lying 
one over the other, as shown in Figures 163 and 164, the 
left portion of one eye lying over the identical left portion 
of the other, and so with the right ; with the upper and 
lower portions of the two eyes, a lies over a, b over b, and c 
over c, and so with other points. If the axes of the eyes (Fig- 
163) be so directed that they meet at a and a, the vision will 
be single, as the identical points will correspond. 

The cause of the impression on the identical points of 
the two retina? giving rise to but one sensation and to the per- 
ception of a single image, is difficult of explanation, and 
various theories have been proposed. It may be due to the 
structural organization of the deeper or cerebral portion of 
the visual apparatus, or may be the result of a mental oper- 
ation; for in no other case is it the property of the corre- 
sponding nerves of the two sides of the body to refer their 
sensations as one to one spot. 

The advantages of binocular vision are: (1) we get a 
larger field of vision than we could with one eye; (2) we 
can more accurately estimate the distance and size of objects ; 
and (3) we have a clearer perception of depth or solidity, 
i. e., a better perspective. 

Distance. — TVe cannot see distance, nor directly estimate 
it with the eye. Various visual sensations enter into our 
judgment of distance. With one eye we perceive distance 
very imperfectly (see Experiment 4). With but one eye we 
have but the sensation of the effect of accommodation; but 
with two eyes we have additional sensations, as the muscular 
efforts caused by the divergence of the eyes, the dissimilarity 
of the two retinal images, the clearness or haziness of the 
images, all of which serve as aids in our determining the dis- 
tance of the object. 

Size and Magnitude. — The estimation of size bears a 
close relation to the estimation of distance, inasmuch as 
our judgment of size depends mainly on the size of the 



412 VISION. 

retinal image, and varies inversely as the distance. Touch 
aids us largely in learning real magnitude. The interven- 
tion of an object of known size, by which we may compare, 
aids much in determining the size of an unknown object. 

Solidity. — Binocular vision is of especial importance in 
our notion of solidity. In looking at a solid object, there 
will be some points in the extreme left of the object that will 
appear in the image of the left eye and not in the right, and 
there will be some points in the extreme right of the object 
that will appear in the image of the right eye and not in 
the left. It is, perhaps, the blending of the impressions from 
these slightly dissimilar images in the two eyes that gives us 
the notion of solidity. 

When an object is too far away for the dissimilar retinal 
images to be appreciated, the relief or solidity must be deter- 
mined by other means, one of the most important of which 
is the distribution of light and shade on the surface. This 
is illustrated by what artists call modeling, as the distant 
mountain made by the gradation of the shades. The forma- 
tion of a single form from two images by means of the 
stereoscope supports the theory that the images of two dis- 
similar pictures, differing much as retinal pictures do, leads 
to the perception of a single object in relief. 

Color Vision and Color Blindness. 1 — When a ray of light 
falls on a prism, it forms what are called the rainbow colors, 
or spectrum. To persons whose color sense is normal, the 
spectrum presents the colors of red, orange, yellow, green, 
blue, indigo, and violet, shading insensibly into one another. 
In the spectrum formed by the sun there are black lines 



i Methods of Testing Color Blindness.— Small skeins of colored wool are used, 
— red, orange, yellow, greenish yellow, blue, violet, purple, rose, brown, and 
gray. There are five finely graduated shades of each of the colors named. In 
testing a person, only one skein is used; e. g., a bright red. The skein being 
placed before him, he is asked to choose the skein most like the one he has. 

By the experiments of Mace and Nacati, it was found that a red-blind per- 
son perceives green light much brighter than a normal person. The green-blind 
person had an excessive sensibility for red and violet. " It appears that what 
the color blind lose in perceptive power for one color, they gain for another." 



COLOR VISION AND COLOR BLINDNESS. 413 

passing through the spectrum which are designated by the 
line a b c, etc. While we cannot here discuss their cause, 
they will aid us in indicating position in the spectrum. 

That we may better understand the nature of color vision, 
let us inquire as to the nature of light. We have many rea- 
sons for believing that light is caused by undulations, or 
waves, of ether, which pervade all space, even the interstices 
between the molecules of substances. 

White light is due to the union of the waves of all vis- 
ible frequency. (See Experiment 10.) Substances differ 
in their absorption power of light, some taking up nearly all 
the light, some but little, while others have absorption power 
only for certain kinds of light. The color of an object de- 
pends on the light it reflects. Transparent objects transmit 
all the light, as white ; but colored transparent objects appear 
of the color of the light which they permit to pass. 

From the experiments we have learned that colors may 
be mixed, producing white. ^N"ot only is this true of the 
colors of the spectrum, but it is also produced by certain 
pairs of colors called complementary colors, as red and green- 
ish blue, yellow and indigo blue. White may also be pro- 
duced by mixing red, green, and violet, which are known as 
fundamental, or primary, colors. 

Each color is characterized by three qualities: (1) its 
hue; (2) its purity, or degree of freedom from admixture of 
white ; and ( 3 ) the brightness, strength, or luminosity. Iden- 
tical colors are those which possess these three qualities in the 
same degree, and appear as such to persons of normal vision. 
There are persons who do not have the power of distinguish- 
ing these three qualities in their true degree, and such per- 
sons are said to be color blind. The more common forms of 
color blindness are red blindness and green blindness. Per- 
sons thus affected are unable to distinguish between green 
and red. A person who is red blind regards certain hues of 
red as green and certain hues of green as white. To a green- 
blind person orange appears a pale red. By a study of the 
diagrams these defects may be studied more thoroughly. 



414 



VISION. 



Violet blindness is somewhat rare, and total color blindness 
very rare. 

Most cases of color blindness are hereditary defects, and 
are incurable. Color blindness may also be produced by dis- 
ease. Various theories have been given to explain color 
sensation, and of these the more satisfactory are those of 
Young and Helmholtz. 

Young's theory (Fig. 165) is based on the fact that 

there are 
three funda- 
mental colors, 
and from this, 
normal vision 
i s considered 
trichro- 
matic ; i. e., 
that there are 
but three col- 
o r sensations. 
theory 




R Y G Bl V 

Fig. 165. — Diagram of the Three Primary Color 
Sensations (Young -Helmholtz Theory). 
1. Red. 2. Green. 3. Violet. The letters indicate the T h 1 S 
colors of the spectrum ; the height of the curve, the extent -, -, -, \ 

to which the several primary color sensations are excited WOUld demand. 



by .vibrations of different wave length. 



(O. W. B.) 



but a few 

varieties of nerve endings to give us a knowledge of colors, 
but we can explain color sensation by having one set of nerve 
endings sensitive to red light, one to green light, and another 
to violet light. 

We have by the modification of Helmholtz what is called 
the Young-IIelmholtz Theory. This theory supposes that 
there are in the retina three kinds of nerve elements, each 
kind being most excitable or most affected by one of the three 
fundamental colors, but also in some degree by each of the 
other two. The combination of these primary sensations in 
varying proportion gives rise to the various colors just as 
in mixing the primary colors in varying proportions we get 
various colors. If the three sensations are of equal intensity, 
white light is perceived. This theory explains color blind- 
ness on the ground that in case of defect of the perception 



DEFECTS OF THE EYE. 415 

of a given color some one of the fundamental elements is 
wanting, as for example in red blindness the fundamental 
red is wanting, and two fundamental sensations are wanting. 
Tt seems, however, that the parts are not entirely insensible 
to red, as red colors excite feebly nerve elements perceptive 
of green. 

The theory also explains color after-images, as by staring 
at any bright object for a short time, the nerve perceptive of 
that color becomes fatigued, and the complementary color is 
seen on looking at a white background. While this theory 
helps us to explain many color sensations, it does not dis- 
tinguish between retinal rest and the sensation of blackness, 
neither have we been able to find the three kinds of nerve 
endings which would make possible the three kinds of fun- 
damental sensations. 

DEFECTS OF THE EYE. 

In the normal (emmetropic) eye, parallel rays are 
brought to a focus on. the retina without the effort of accom- 
modation. All objects over twenty feet away can be seen 
without any effort of accommodation ; i. e., the far point 
of the normal eye is an infinite distance, and it is in viewing 
near objects that we have to call into use accommodation, in 
order to see the objects clearly. 

The eye may be so constructed that rays from objects 
very near the eye are focused, while those from objects a 
short distance away are not, and the object becomes indis- 
tinct or is not seen at all. This condition is known as 
short-sightedness (myopia). The cause of this defect is 
an abnormal elongation of the eyeball, and quite frequently 
the eye is also larger, and probably the lens is more convex. 
As a result the rays are brought to a focus in front of the 
retina (Fig. 161), so that we have either a very indistinct 
image or none at all. 

From our experiment you can easily understand how 
this can be overcome by the use of concave glasses. The 
opposite condition may also exist; the eyeball is too short, 
and as a result parallel rays are not brought to a focus when 



416 VISION. 

they reach the retina. To focus parallel rays, an effort of 
accommodation is required, as from distant objects, and for 
far objects, very great effort is required. It will be seen from 
this that the ciliary muscles are constantly acting. 

This condition is known as long-sight (Fig. 163) (Jiyper- 
metropia). From our experiment, you can readily see why 
convex glasses are used to render the light more convergent, 
and thus correct the defect. 

In order that the rays of light be properly focused, it 
is necessary that the lens have the same curve along all its 
meridians, for if less curved or greater curved along one 
meridian than along the other, it would make the ray at 
that part more or less divergent, and therefore an imperfect 
focusing of the rays, producing an imperfect image. In the 
eye, as a result of this defect, lines in one direction may 
be seen clearly, while those in another direction will be 
blurred. The eye may be myopic in one place, and hyper- 
metropic in others. This defect is known as astigmatism, 
and is usually due to an unequal curvature of the cornea, 
but occasionally may be due to a defect of the crystalline 
lens. To correct the difficulty the glasses have to be especially 
ground, which requires great care on the part of the optician 
in his measurement. 

The rays of light which fall upon the outer field of the 
lens are not brought to a focus at the same point as those 
which fall upon the central portion of the lens, owing to their 
unequal refraction. This defect is known as spherical aber- 
ration. 

In a microscope, camera, and other optical instruments 
it is prevented by putting on the front of the lens a screen 
with a circular opening, so as to shut off the rays from the 
outer field, and allow only those to pass which are near the 
center. As has been suggested, the correction for aberration 
in the eye is made by the iris. The posterior part of the 
iris is covered with pigment to prevent the passage of light 
through its substance, thus shielding the light from all parts 
of the lens except parts back of the pupil. 



DEFECTS OF THE EYE. 417 

The image will be best defined when the pupil is small 
and the amount of light is abundant, but the eve is so con- 
structed that even when the pupil is much dilated, as in 
feeble light, the image may be quite well defined. 

Distinctness of vision is further secured by the pigment 
of the outer surface of the retina and posterior surface of 
the ciliary processes. These pigments absorb any light that 
might be reflected within the eye, and prevent its being 
thrown again upon the retina to interfere with the image 
formed there. Were it not for this pigment, as the layer 
of the retina is very transparent, and if the opposite sur- 
faces had the power of reflecting the rays, they would fall 
upon other parts of the membrane, producing both dazzling 
from excessive light, and indistinctness of the images. 

When a ray of light is passed through a prism, it is not 
only refracted, but it is separated into its elementary colors. 
When a ray of light is passed through an ordinary convex 
lens, a similar separation of the light into its elementary 
colors takes place, giving to the images formed, colored mar- 
gins. This is due to the difference in wave length of the 
different kinds of light; they are therefore refracted differ- 
ently, and do not focus at the same point This defect in 
optical instruments is called chromatic aberration. It is 
corrected in lenses by having them made of separate parts 
and different kinds of glass (as crown glass and flint glass), 
and so ground as to equalize the refraction of the different 
kinds of light, thus preventing a coloring of the image. 
Such lenses are called achromatic. 

In the human eye this is probably overcome by the un- 
equal refracting power of the refracting media in front of 
the retina. The eye is only achromatic when the image is 
received at its focal distance upon the retina, or so long as 
the eye has the power of accommodation. If either of these 
conditions be interfered with, more or less chromatic aberra- 
tion appears. It is stated by Helmholtz that a small white 
object cannot be accurately focused on the retina; if we 
focus for the red rays, the violet are out of focus, and vice 
27 



418 VISION. 

versa; and when not exactly focused, they are seen sur- 
rounded by pale yellowish or bluish fringe. 

Red rays being less refrangible, a stronger effort of ac- 
commodation is necessary to focus them, and the eye being 
adjusted as if for nearer objects, red surfaces appear nearer, 
while blue, requiring less effort (due to their greater refran- 
gibility), appear farther away. From the imperfect adjust- 
ment of a small, white object it appears to be surrounded 
by a kind of halo. This appearance is called irradiation. 

From the same cause a white square on a black ground 
appears larger than a black square of the same size on a 
white ground. 

The long-sightedness of old age (presbyopia) is due to 
gradual loss of the power of accommodation, which is due 
chiefly to the gradual increased density of the lens, by which 
it is unable to become convex, and also to a weakening of the 
ciliary muscle and a general loss of elasticity of the parts. 

Visual Sensations. — Light is the normal agent in excita- 
tion of the retina. The only layer of the retina capable of 
responding to this stimulus consists of the rods and cones. 
The following are some of the most important proofs of this 
statement : — 

1. The point of entrance of the optic nerve has no rods 
or cones, and is insensitive to light. 

2. The fovea centralis of the macula lutea is most sen- 
sitive to light, although it contains no optic nerve fibers. 
In the fovea, cones only are found, while in other parts of 
the retina rods are more numerous than cones. 

3. The phenomena of Purkinje's figures are due to the 
shadows of the retinal vessels cast by the candle. The 
branches of these vessels are chiefly distributed to the nerve 
fibers and ganglionic layer ; and since the light of the candle 
falls on the retinal vessels from in front, the shadow is cast 
behind them, and thus those elements of the retina which 
perceive the shadows, must lie behind the vessels. This 
seems to be a clear proof that the light-perceiving elements 
of the retina are not the fibers of the optic nerve forming 
the innermost layer of the retina, but the external layers of 



VISUAL SENSATIONS. "±19 

the retina, rods, and cones, which appear to be special ter- 
minations of the nerve fibers. 

Duration of Visual Sensation. — The duration of the sen- 
sation produced by a luminous impression is always greater 
than that of the impression which produced it. Nd matter 
how brief the impression, the effect on the retina lasts for 
about one eighth of a second. Thus a rotating stick when 
turned rapidly appears as a continuous circle. After a cer- 
tain rate, the impressions, by their persistency, become fused 
in appearance. The after sensation of an impression varies 
directly as the intensity. As for example, looking at a bright 
object for some time, and then looking away, when the object 
may be perceived for some time. 

Intensity of Visual Sensation. — It might seem at first 
thought that the intensity would vary as the intensity of the 
light. But this is not the case. Light must have a certain in- 
tensity before it can excite the retina, but it is impossible to 
fix an arbitrary limit to the power of excitability. The effect 
is not directly proportional to the increase of excitation, but 
it is, according to the law formulated by Fechner, as the 
logarithm of the stimulus. This law is only true within 
certain limits. When the retina is stimulated by the light 
of one candle, the light of two candles will produce a differ- 
ence in sensation that will be distinctly felt. If, however, 
the first stimulus be that of an electric light, the addition 
of one candle would make no difference in the sensation. So 
if the first stimulus is small, a small increase will be 
noticed; but if the first stimulus be great, it will require a 
proportionally greater stimulus to be perceived. The stim- 
ulus increases as the ordinary numbers ; the sensations, as 
the logarithm. 

How the Retina Is Stimulated. — The method by which 
the retina x is stimulated, so that the visual sensation is per- 

iThe more important changes produced in the retina in vision are: — 
1. Bleaching of the visual purple. This lias also been found in the inner 
segments of the cones. The colored bodies (chrnmophanus) are represented as 
oil lobules of various colors: red (rhodophan) , gr^en (chlorophan), yellow (xantho- 
phan). They are not found in mammals. The visual purple seems to be 
derived in some way from the retinal pigments, as it will not be formed if the 
retina be detached from the pigment layer. 



420 VISION. 

ceived by the cerebrum, is not understood. It is thought 
that the light produces a chemical change in the protoplasm, 
and that this change stimulates the optic nerve ending. 

Some light was thrown upon the nature of this change by 
the discovery of a temporary reddish-purple pigment (rhodo- 
plasm or visual purple) of retinal rods. In experimenting on 
the frog it is found that the pigment disappears on exposure 
of the retina to the light, and reappears when the light is 
removed, and also that there are distinct changes in the visual 
purple when other than white light is used. 

The visual purple is almost absent from the retinal cones, 
from the macula lutea, and from the fovea centralis of the 
human being, and it does not appear to exist at all in the 
retina of some animals, as the bat, dove, chicken, all of which 
have good vision. From this it seems that it is not essential 
to vision. While this is true, it is without doubt one of the 
changes important in reproducing vision. 

Why the Object Is Seen Erect. — The retinal image is 
inverted. Why, then, do we see the object erect? The 
visual centers, like other centers, refer their impression to 
the exterior. This power is called sense projection. We do 
not say the sound is in the ear, but exterior to the ear from 
the sonorous body ; the taste is not in the tongue, but in the 
sapid substance; and so with vision, the impression is not 
referred to the retinal image, but to the object that produced 
it, and as it is erect, the sense impression is the same. The 
fact is, we take no more conscious notice of the retinal image 
than we do of the changes which take place in rods of Corti 
in sound perception. The statement that we at first conceive 
of the object as inverted, and by acquired perception train 
ourselves to see objects erect, is untrue. 



granules of the pigment cells which overlie the outer part of the rod and cone 
layer of the retina become diffused into the parts of the cells between rods and 
cones, the granules (melanin, orfuscin granules) passing down into the processes 



2. There is a movement of the pigment cells. When stimulated by light, the 
" the pigment cells which overlie the outer part of the rod 

retina become diffused into the parts of the cells betw 
_ CT ranules (melanin, or fuscin granules) rjassing down into 1 
of the cells. 

3. There is a movement of the cones, and it may be of the rods, too, on stim- 
ulation of the outer parts of the cones which, when not affected by the light, 
extend into the pigment layer, and are refracted. It is thought by some that 
this contraction is under control of the nervous system. 

4. The researches of Dewar, McKendrick, and Holmgren give reason to believe 
that the stimulus of light produces a variation of natural electrical currents 
of the retina, which at first increase and then diminish. McKendrick thinks 
these electrical currents are the result of the chemical changes which we have 
mentioned as taking place in the retina. 



1 2 




PLATE XVII. 
Fig. 1C4. — A Diagram to Illustrate Nervous Apparatus of Vision in Man. 

(From Ranney.) 

The lines < A and B) indicate the fibers associated with the left cerebral hemisphere. Those 
of the right hemisphere (u and D) appear as separate lines. Both will be seen in the diagram to 
pass from the retina through the following parts: the optic nerves; the crossing fibers through 
the optic chiasm, theiootic tracts; the external geniculate body; the corpora quadngemina or the 
" pulvinar " of the optic thalamus; and the internal capsule. The fibeis are shown to end in the 
cortex of the occiiatal lobes. 

A lesion situated at the points designated as 1. 2. 3, 4, and 5, will cause homonimous 
hemianocin. Lesions of the right hemispher< of the cerebrum produce blindness of the right 
ha f of each eye, and vice versa. 



CHAPTER XIX. 
HEARING. 

EXPERIMENTS AND DEMONSTRATIONS. 

1. Hold a watch between the teeth, or touch the upper 
incisors with a vibrating tuning-fork; close both ears by 
means of the finger. Do you hear the tick of the watch or 
the sound of the tuning-fork ? Xow unstop one ear. What 
difference do you note ? How do you account for what you 
observe ( 

•2. Hold the tuning-fork to the incisor 'teeth until you 
can no longer distinguish the sounds. Xow close both ears. 
How do you account for the difference ? 

3. Listen to a tuning-fork set to vibrating by means of 
electricity, or to a watch ticking. Close the mouth and nos- 
trils, and take a deep inspiration or deep expiration, so as to 
change the tension of the air in the tympanum. What differ- 
ence do you note in the intensity of the sound ? Explain the 
difference. 

4. Suspend an iron poker by means of a string, wrap the 
end of the string so as to be about ten inches from the end 
of the poker, place the finger to which the string is attached 
in the ear, and strike the poker against a table or chair. 
Compare the sound made by striking it when the finger is 
not in the ear. What makes the difference ? Also suspend 
a two- or three-pound weight by a stout string; tie free end 
around the finger so as to be two feet from the weight. Place 
the finger in the ear as before. Xow strike the string, with 
the finger in the ear. Strike the string, with the finger out 
of the ear. What difference do you note ? Explain differ- 
ence. Vary length of the string. What effect has it on the 
pitch of the tone ? Keeping the string of the same length, 
vary the weight. What effect has the increased tension? 

5. Test a blindfolded person for his ability to judge of 
the direction of sound by snapping two coins together directly 
in front, directly behind, to the left, to the right, over the 
head, etc. Xotice carefully the movements of the head. 

421 



422 HEARING. 

6. Press both auricles against the side of the head, and 
hold both hands vertically in front of each meatus; have 
some one make a noise in front of you, and you will judge 
of the sound as coming from the opposite direction. 

7. By examination of the outer ear, determine the names 
of its parts by comparison with Fig. 166. 

8. Examine a model of the ear, and learn the parts' by 
comparison with Fig. 166. 

9. From the head of a rabbit or rat, saw out the portion 
of the temporal bone containing the ear for half of an inch 
on each side of the opening (meatus auditorius externus) to 
the ear. Put in different grades of alcohol as directed in 
the Appendix. When hardened, put in dilute acid for several 
days to remove the mineral matter of the bone. Wash thor- 
oughly, and imbed in celloidin, and make section, mount 
in balsam, and examine. Examine some of the section with 
low-power lens (twenty to thirty diameters). 

HEARING. TEXT. 

The organ of hearing is the ear. It consists of three 
parts : the external ear, the middle ear, and the internal ear. 

The External Ear. — ■ The external ear consists of two 
parts, the outer expanded portion, the pinna and the canal, 
or the external meatus. The pinna is composed of a thin 
plate of yellow cartilage covered by the skin, presenting emi- 
nences and depressions, the specific names of which may be 
learned from Fig. 166. The lobule of the pinna is free from 
cartilage. The pinna is united to the surrounding parts by 
ligaments and muscular tissues. The muscles of the ear 
are, one for raising the ear (attollens aurem), one drawing 
it forward and upward (attraliens aurem), one drawing it 
backward (retraliens aurem). In man these muscles have 
little action, but in some animals they are functional, and 
move the ear so as to direct its concavity in the direction of 
the sound, thus enabling the pinna to better collect the sound. 
The external meatus is about one and one fourth inches in 
length; its outer part is cartilaginous, its inner part bony. 
The skin in the deeper cartilaginous parts becomes more deli- 
cate and vascular, and contains a modified form of sweat 



STRUCTURE OF THE EAR. 



423 



glands called ceruminous glandsj which secrete a wax {ceru- 
men). 

The Middle Ear, Tympanum This is an irregular 

cavity (Fig. 166) in the temporal bone filled with air, 
received from the pharynx by means of a tube (Eustachian 
tube), which leads from it to the middle ear. The roof of 




Fig. 166. — General View of the Ear. 

1. Helix. 2. Anti-helix. 3. Tragus. 4. Anti-tragus. 6. Lobule. 1, 2, 3, 4, and 
6. Pinna. 6. Meatus (auditorius externus). 1,2, 3, 4, 5, and 6. External. 7. Mem- 
brana tympani (drum of the ear). 8. Tympanum (middle ear). 9. Temporal 
bone. 10. Malleus. 11. Incus. 12. Stapes. 10, 11, 12. Bones (ossicles) of the middle 
ear. 13. Portion of temporal bone. 14. Eustachian tube. 15. External semicir- 
cular canal. 16. Posterior semicircular canal. 17. Superior semicircular canal. 
18. Cochlea (turned down to show semicircular canals). 19. Vestibule. 20. Audi- 
tory nerve. (In the diagram the diameters of the middle and internal ear are 
larger in proportion to external than they should be; this is done to make the 
parts plainer. The cochlea is turned down to show the semicircular canals and 
auditory nerve.) 

the middle ear, or the tympanum, as it is sometimes called, is 
formed by a thin plate of bone which separates it from the 
cranial cavity. Its floor is formed by a layer of the temporal 
bones. Its outer wall is formed by a membrane (membrana 
tympani), closing the meatus, composed on its outer part by 
the skin, and on the inner part by muscle fiber and mucous 
membrane, and also by the ring of bone to which the mem- 
brane is attached, 



424 HEARING. 

There are two small openings in the membrane for the 
exit of vessels and entrance of a nerve (the chorda tympani). 
This nerve is a branch of the seventh cranial nerve, and sends 
branches to the submaxillary glands and tongue. By some 
the branch which goes to the tongue is considered as the 
nerve of taste. The membrane of the tympanum is placed 
obliquely at the end of the external meatus. It is about one 
third of an inch in diameter. It bulges in somewhat, 
toward the tympanic cavity. To its inner surface is attached 
the handle of the mallet bone (malleus). On the outside, the 
drum of the ear is pressed on by the external air through 
the meatus, and on the inside by the air entering the tym- 
panic cavity through the Eustachian tube, which ordinarily 
is closed; and if closed, any change in the pressure would 
lead to a bulging in or out of the membrane, as pressure is 
greater or less on the outside than on the inside. 

The air pressure is kept equal by the Eustachian tube 
opening during every act of swallowing, admitting or letting 
out air as is needed to restore the equilibrium of pressure. 
The membrane being more or less on a tension, responds to 
the vibration of the air, and its peculiar structure and form 
enables it to receive tones of a great variety of pitch. 

The inner wall of the tympanic cavity is osseous, except 
two apertures, which are closed by a membrane, one (fenestra 
ovalis) is connected with the vestibule of the inner ear, and 
the other (fenestra rotunda) is connected with the chochlea 
of the inner ear. 

On the inner wall may be noted a bony prominence, the 
promontory between the two openings, a curved bony canal 
(aqueducts Fallopii), and a conical bone (pyramid) from 
which a muscle passes to the stapes. On the anterior wall is 
a canal containing the muscle (tensor tympani), which tight- 
ens the membrane, and is inserted in the upper part of the 
handle of the malleus. 

On the anterior wall is the opening of the bony portion 
of the Eustachian canal. This canal, which is lined through- 
out with mucous membrane, and opens into the pharynx, 



STRUCTURE OF THE EAR. 425 

serves principally, as has been stated, to keep the pressure 
within and without the tympanum the same by the act of 
swallowing, which often takes place unconsciously, even 
when not eating. The entire tympanic cavity, as well as 
that of the Eustachian tube, is lined with mucous membrane, 
having ciliated cells. The ciliated cells, however, are not 
found on the tympanic membrane. 

Bones of the Middle Ear. — A chain of three bones 
(ossicles) stretches across the tympanum from the membrana 
tympani to the fenestra ovalis. The first in the chain is the 
hammer (Fig. 166) (malleus). By its rounded head it 
articulates with the anvil, and by its vertical process or handle 
(manubrium) it is firmly attached to the fibrous layer of the 
membrana tyrapani, and to its inner and upper part is 
attached the tendon of the tensor tympani, by the contrac- 
tion of which the handle is drawn, thus increasing the ten- 
sion of the tympanic membrane. From the upper part of 
the handle passes a long slender process (processus gracilis) 
to a fissure in the bony wall, to which it is connected by lig- 
amentous fibers. Another ligament also passes from the roof 
of the tympanum to the head of the malleus. 

The second in the chain is the anvil (incus). In form it 
is more like a bicuspid tooth with widely separated fangs than 
like an anvil. The short process (processus brevis) lies hor- 
izontally, and is attached to the inner wall of the tympanum 
by a ligament. The longer process lies vertically parallel to 
the handle of the malleus, and is articulated to the stapes. 
The articulation between the head of the malleus and the 
body of the incus is of a peculiar saddle shape, the lower 
part of the articular surface of each bone having a blunt, 
tooth-like process, so that, when the hammer is drawn in- 
ward by the handle, it bites the anvil firmly, and carries it 
with it, but when the tympanic membrane with the hammer 
is driven outward, the anvil is not obliged to follow it. By 
this provision the stirrup is prevented from being pulled out 
of the fenestra ovalis by any undue push on the tympanic 
membrane. The lower end of the long process of the incus 



426 HEARING. 

bends inward, and ends in a small, flattened bone (os orbi- 
cular e) which articulates with the head of the stapes. In 
early years the os orbiculare is a separate bone, but it be- 
comes joined to the incus in the adult. 

The stirrup (stapes) lies horizontally at right angles to 
the long process of the incus, and its bony foot plate, covered 
internally with cartilage, is attached to the margin of the 
fenestra ovalis. 

To the head of the stapes is inserted the small stapedius 
muscle, which arises from the inner tympanic wall through a 
hole near the fenestra ovalis. It is this muscle that regu- 
lates the movement of the stapes, preventing undue pressure 
on the labyrinth, and it may be considered as antagonistic 
to the tensor tympani. 

The chain of bones thus formed is bound together and 
secured by ligaments, and may be regarded as a bent lever 
round an axis passing through the lower end of the neck of 
the malleus, the power being applied at the end of the handle 
of the malleus, and the effect being felt at the foot plate of 
the stapes; sound vibrations pressing in on the tympanic 
membrane press in on the handle of the malleus, causing its 
head, together with the body of the incus, to move outward, 
while the outward motion of the body of the incus causes its 
vertical process to have an inward movement that presses 
the base of the stapes into the fenestra ovalis against the 
liquid of the labyrinth. As the vertical process of the incus 
is only two-thirds the length of the first arm of the lever, the 
inward movement of the stapes will be only two-thirds that 
of the handle of the malleus, though the pressure exerted 
by the stapes will be one half greater. The area of the tym- 
panic membrane is about twenty times that of the fenestra 
ovalis. This makes a relative large movement of small 
intensity by the tympanic membrane and chain of bones, one 
of smaller movement but of greater energy. 

The Internal Ear. — The internal ear, or labyrinth (Fig. 
166), is formed of tubes and cavities hollowed out in the 
temporal bone, and is inclosed on all sides, except openings of 



STRUCTURE OF THE EAR. 



427 



the fenestra rotunda and the fenestra ovalis, on the exterior, 
and apertures for the branches of the auditory nerve and 
blood vessels on the interior. It consists (1) of the bony, or 
osseous, labyrinth formed in the petrous portion of the tem- 
poral, and (2) of the membranous labyrinth contained within 
the osseous labyrinth. Between the osseous labyrinth and the 
membranous labyrinth is a liquid called the perilymph, and 




Fig. 167. — Internal Ear. 
1. Semicircular canals. 2. Ampulla. 3. Utricle. 4. Saccule. 5. 
Cochlea. 6. Duct of the utricle. 7. Endolymph duct. 

within the membranous labyrinth is another liquid called 
the endolymph. 

The bony labyrinth consists of three parts : 1. The vesti- 
bule is the central cavity, and has on its outer wall the 
fenestra ovalis, which is closed by the footplate of the stirrup 
bone, and also in its anterior wall is found the fenestra ovalis. 
On its inner walls are two depressions (fovea?), separated 
by a ridge. Behind it communicates by five openings with 
the semicircular canals, one orifice being common to two of 
the canals. 2. The semicircular canals, which are situated 
above and behind the vestibule, lie in three planes, one hori- 
zontal, two vertical, and at right angles to each other, like 
the three adjacent sides of a cube, the external horizontal 
canal opening by two distinct openings into the vestibule. 
The semicircular canals are about one twentieth of an inch 
in diameter, and end in a dilation at one end called the am- 



428 HEARING. 

pulla. 3. The cochlea is situated in front of the vestibule; 
in its form it resembles a small snail shell. Its parts are, a 
bony canal about one and one-half inches in length, and a 
central column called the modiolus, around which the canal 
winds spirally two and one-half times. 

In the dry state the bony canal is partly divided into two 
canals by a thin bony plate (the lamina spiralis) projecting 
from the modiolus. In the fresh state there passes from 
the edge of the bony plate a membrane (the basilar mem- 
brane), which completely divides the coiled tube of the coch- 
lea into two parts (scalce), the upper one being called the 
stairway of the vestibule (scala vestibuli); as it starts from 
the vestibule, and winds around to the apex of the coil, the 
lower part is called the stairway of the tympanum, and is 
shut off from the tympanic branch by the membrane of the 
fenestra rotunda; it communicates with the upper space at 
the apex by a tiny hole (the helicotrema) . A fine connective 
tissue membrane (membrane of Reissner) passing from the 
lamina spiralis to the bony wall of the cochlea forms in the 
small triangular part of the scala vestibuli a duct, called the 
central canal of the cochlea, or scala media. The bony tu- 
bular canal of the cochlea is thus divided into three canals 
(Fig. 168). 

The Membranous Labyrinth The membranous laby- 
rinth is a closed membranous tube, lined with epithelium 
and filled with endolymph, and having the same general 
form as the bony labyrinth in which it lies. The bony ves- 
tibule contains, however, two sacs, the utricle and the saccule. 
The membranous semicircle canals open into the utricle. 
They are adherent along one side of the bony canals, but are 
only one third the diameter of the bony canal. Each of the 
membranous canals is dilated when it opens into the utricle, 
the expanded portion being called the ampulla. There is 
no direct connection between the utricle and saccule, but they 
connect indirectly (by the saccus endolymphaticus) , arising 
by an isolated limb from each sac, the limbs uniting in the 
form of a Y, the terminal sac lying in the skull. From the 



NERVES OF THE EAR. 



429 




1 
Fig. 168.— Structure of Cochlea. 
1. Cochlear branch of the audi- 
tory nerve. 2. Lamina spiralis. 3- 



membranous saccule a narrow tube (the canalis reuniens) 
leads into a small central canal (scala media) of the cochlea 
which is the cochlea portion of the membranous labyrinth 
and lies between the two scalse. 

By the system of canals just mentioned, the various parts 
of the membranous labyrinth are placed in communication, 
and thus the endolymph of one portion may mingle with that 
of another. Around the mem- 
branous labyrinth are the por- 
tions of the bony labyrinth not 
cut off by membrane and occu- 
pied by perilymph, the peri- 
lymph of the bony vestibule 
being continuous on the one hand 
with that in the bony semi- 
circular canals, and on the other 
hand with that of the scala 

..77. ljl 1 .1 7 7* wij ucxtc u. ijaiuiiia opiiana. 

vestlOUll, and through the het%- Scala tympani. 4. Ductus coch 
. -1,1 ■ ,i 7 learis. 5. Scala restibuli. 6. Modi- 

cotrema with that in the scala oius. 
tympani. 

The Auditory Nerve. — This nerve enters the bony canal 
(the meatus auditorius intemus) with the facial nerve and 
the nervous intermedins, and on leaving the bony canal, 
enters the labyrinth at the angle between the base of the 
cochlea and vestibule in two divisions, one for the vestibule 
and semicircular canal, and one for the cochlea; the branch 
going to the vestibule divides into two branches, one, the 
superior, distributed to the utricle and to the superior and 
horizontal semicircular canals, and the inferior, ending in 
the saccule and posterior semicircular canal. In both 
branches are numerous ganglionic nerve cells. The fila- 
ments derived from the cochlear branch of the auditory 
nerve pass up the axis of the cochlea, and give off fibers of 
the spinal lamina, at the base of which is the small spiral 
ganglion containing bipolar cells. From the edge of the 
spiral lamina the fibers pass to join with the organ of Corti 
(Fig. 169). 



430 



HEARING. 



The Auditory Nerve Endings. — The membranous laby- 
rinth is lined by an epithelium resting on a basis of connect- 
ive tissue, the epithelium being modified in certain places to 
receive the nerve endings to form the nervous end organ of 
hearing. In the utricle the nerve fibrils are joined with an 
area of modified epithelium, forming an oval swelling (called 
the macula acustica) ; a similar area is found in the saccule. 
In each ampulla the epithelium is also modified where the 




Fig. 169. — Section through One of the Coils op the Cochlea. 
1. Scala vestibuli. 2. Stria vascularis. 3. Limbus laminse spiralis. 4. Sulsus 
spiralis. 5. Membrana tentoria. 6. Membrana vestibuli (Reissner's membraiie). 
7. Canal of the cochlea. 8. Basilar membrane. 9. Ligamentum spiralis. 10. 
Scala tympani. 11. Lamina spiralis (ossea). 

fibers terminate, forming a horseshoe-shaped ridge (the crista 
acustica). The vestibular branch of the auditory nerve ends 
in the macula acustica of the utricle, the macula acustica 
of the saccule, and the crista of each of the three mem- 
branous ampullar In these various areas the modified epi- 
thelium is mainly formed of columnar cells, which end in 
a tapering process, called auditory hairs (Tigs. 169), and 
to these hair cells of the macula? and cristse the naked 
axis-cylinders of the nerve pass, entering, according to some 



NERVES OF THE EAR. 431 

authorities, the very substance of the cell itself. Between 
the columnar hair cells are a number of thin nucleated rod- 
like cells (fiber cells), which serve as a support. The free 
ends of the auditory hair are covered by a cap of mucous 
substance floating in the endolymph, and in the utricle and 
saccule this viscid endolymph contains small crystals, con- 
sisting principally of carbonate of lime, called otoconia, or 
otoliths. They probably serve as dampers. 

The cochlear division of the auditory nerve passes into a 
small bony channel running up the modiolus, or the central 
column of the cochlea, giving off branches to the lamina 
spirals to be distributed as base axis-cylinders to the hair- 
like cells of the organ of Corti in the scala media. The floor 
of the spiral triangular tube of the cochlea is partly formed 
by the extremity of the spiral lamina and partly by the 
basilar membrane, which stretches from the end of the bony 
lamina to the outer wall of the cochlea, being attached to 
it by a structure of connective tissue called the spiral liga- 
ment. As the basilar membrane passes from the base to 
the apex of the cochlea it increases in breadth. It is com- 
posed of fibers which extend radially from within outward, 
and lias on its upper surface, inside the central cochlear 
canal, modified epithelium, called the organ of Corti. 

The Organ of Corti (Fig. 169) consists (1) of the rods 
of Corti, placed in about the middle of the organ. These are 
arranged along the spiral canal, in an inner and outer row, 
and consist of peculiarly modified epithelial cells, their bases 
resting apart on the basilar membranes, but their heads lean- 
ing against each other, like the rafters of a house. The series 
of arches thus formed by the two sets of rods forms a tunnel 
running along the length of the cochlear canal. The head of 
each rod gives off a process projecting outward, those of the 
inner row overlapping those of the outer, the inner rods, 
however, being one half more numerous than those of the 
outer rods, the heads of the two outer rods fit into three of 
those in the inner row, and when viewed from above by the 
microscope, the head plates of the rods of Corti resemble the 



432 



HEARING. 



keyboard of a piano. (2) The inner hair cells, which are 
placed on the inner side of the inner rods, form a single col- 
umnar series, from the upper ends of which project a num- 
ber of short auditory hairs, arranged in a crescent form, and 
their pointed bases rest among long nucleated cells, that 
appear to serve as supporting structure. (3) Those placed 
on the outer side of the outer rods, called the outer hair cells. 
They resemble the inner hair cells, having, like them, short 
hairs arranged in crescent form on the upper surface, and 

arranged, in man, in 
four rows. The sup- 
porting cells are on the 
outside of each of the 
outer hair cells, and are 
without hairs, and are 
called cells of Belters. 
(4) Stretching like a 
network over the outer 
cells is a membrane 
called reticular mem- 
brane, composed of 
three series of fiddle- 
shaped rings united to- 
gether by flat bars. The 
heads of the outer hair cells pass through the holes of the 
rings while the processes from the cells of Deiters are at- 
tached to the bars between the rings. 

A soft, elastic structure {tectorial membrane) that arises 
from the upper lip of the peculiarly formed piece of connec- 
tive tissue, called the limbus at the edge of the bony spiral 
lamina (Fig. 168), overhangs the organ of Corti. By some 
authorities it is considered to be a damping apparatus for 
the organ of Corti. 

The fibers of the cochlear nerve pass out from the spiral 
lamina after traversing the ganglionic bipolar cells of a 
small ganglion (ganglion spirale) situated in the bony lam- 
ina. On leaving the lower lip of connective tissue tipping 




Fig. 170. — Auditory Hairs. 
1. Auditory hairs. 2. Limitans acusticae. 
3. Hair cells. 4. Nerve fibers. 






HOW WE HEAR. 433 

the spiral lamina they lose both their primitive and medul- 
lary sheaths, and pass as naked axis-cylinders to the hair 
cells. Most of the fibrils from these axis-cylinders do not 
appear to pass directly to the hair cells, but run some dis- 
tance along the length of the cochlear canal in spiral strands 
at the base of the inner hair cells, or in the tunnel of Corti, 
or along the bases of the outer hair cells. Finally, however, 
the fibrils become connected with the hair cells, though there 
is doubt as to their passing into the cells, or perhaps they 
merely invest the cells. It is considered as settled that the 
inner and outer hair cells are the true terminal organs of 
the auditory nerve in which the sensory impulses that pass 
to the brain originate, and that the other parts of the organ 
of Corti are merely accessory in function, assisting in some 
way the nervous impulses, but not actually giving rise to 
them. 

How We Hear. — The sound waves, which are collected 
by the pinna of the external ear, pass by the external meatus 
to the tympanic membrane, which is set in vibration, and, 
by its peculiar form and structure and being somewhat 
loosely and unequally stretched and loaded by the tympanic 
bones, is capable of taking up sonorous vibrations of various 
rates. These vibrations are transmitted onward by the chain 
of bones swinging as a whole and acting as a lever. With 
diminished amplitude, but increased force, the base of the 
stapes communicates the vibrations to the whole mass of peri- 
lymph in the vestibule, from which the vibrations pass 
along the scala vestibuli and down the scala tympani to end 
on the fenestra, the rotund membrane of which moves out- 
ward as the fenestra ovalis moves inward, and conversely. 

As the vibrations pass up the scala vestibuli, they are 
also transmitted across the membrane of Reissner to the 
endolymph of the central cochlear canal and the basilar 
membrane, affecting in some way the auditory epithelium 
or hair cells of the organ of Corti, and thereby the termina- 
tions of the cochlear nerve. The vibration of the perilymph 
of the vestibule is also transmitted through the membranous 
28 



434 HEARING. 

labyrinth to the endolymph of the utricle saccule and mem- 
branous semicircular canals, to reach the epithelium 1 of 
the maculae of the utricle and saccule and that of the cristas 
of the ampullae, affecting the terminal filaments of the 
vestibular nerve. 

Vibrations may also be transmitted by the bones of the 
skull to the tympanic membrane, and onward by the chain 
of bones to the internal ear. The sound of a tuning fork 
may be heard by holding the fork between the teeth, the 
vibrations passing into the labyrinth through the bones of 
the skull, and affecting the auditory nerve, even when the 
tympanic membrane is injured. 

The most highly specialized of the auditory apparatus 
is the organ of Corti, and it is therefore the chief agent in 
hearing. In order to understand more fully how we hear, 
let us give a more careful study of how the sonorous vibra- 
tions reach the hair cells of the organ of Corti. 

A sound from a musical instrument or the human 
voice has a certain quality, or timbre, due to the blend- 
ing of the fundamental tone (which determines the pitch) 
with the partial upper tones, which vary in number and 
intensity in different instruments. Thus the sound goes to 
the ear as a complex one. It is possible to analyze a com- 
posite sound by raising the dampers of a piano, and allow- 
ing the musical sound to be tested, to resound before it, 
when there will be a set of strings brought into sympathetic 
vibrations, that is, those strings which correspond in pitch 
to the fundamental tone and to the several upper tones of 
the note to be analyzed. Now suppose we were able to con- 
nect every string of a piano with a nervous fiber in such a 
manner that this fiber would be excited, and experienced 
a sensation every time the string vibrated. Then every 
musical tone which impinged on the instrument would ex- 
cite (as we know really to be the case) in the ear a series of 
sensations exactly corresponding to the pendular vibration 
into which the ^original motion of the air had to be resolved. 
By this means, then, the existence of each partial tone 



HOW WE HEAR. 435 

would be exactly so perceived as it is really perceived by 
the ear. But the ear has not the power of thus analyzing 
complex sounds, and cannot appreciate the pitch and qual- 
ities of tones ; what part, then, of the auditory apparatus is 
it that is capable of being set into sympathetic vibration by 
the various complex waves of sound ? It has not been long 
since it was thought that the rods of Corti, which vary regu- 
larly in the length and span of their arch from the base to 
the apex of the cochlea, served as an apparatus of sym- 
pathetic vibration for the analysis of sound, each pair 
vibrating in response to a particular simple tone, and stim- 
ulating a particular simple nerve fibril or group of nerve 
fibrils. But their number and variation in size and form 
do not meet the requirements for the wide range in pitch 
and quality of their capability of recognizing. In birds, 
that have without doubt appreciation of musical tones, there 
are no rods of Corti in their rudimentary cochlea, though 
hair cells lie in contact with the basilar membrane. It is 
now generally believed that the stretched radial fibers of 
the basilar membrane, on which the organs of Corti rest, 
are the vibrating threads which have the power of analyzing- 
complex sounds; the rods of Corti assisting in the trans- 
mission of the vibration of the basilar membrane to the hair 
cells, and possibly acting as dampers, also, just as the chain 
of tympanic bones serves both purposes. 

There are about twenty-four thousand fibers in the 
basilar membrane, their length varying from .075 mm. at 
the base to .126 mm. at the apex of the cochlea, and their 
tension probably being changed by the action of what appear 
to be muscular cells in the outer ligament of the membrane. 
It seems, then, that we have in this apparatus one that is 
adapted to appreciate pitch, and to the analysis of complex 
sounds. A single vibration reaching the ear excites by sym- 
pathetic vibration the fibers of the basilar membrane tune 
to the same pitch as the exciting sound, the shorter fibers 
near the base of the cochlea vibrating to the higher notes, the 
longer fibers of the apex of the cochlea vibrating to the lower 



436 HEARING. 

notes; and the different fibers tuned to difference of pitch 
affect in some way different auditory cells, which in their 
turn affect different nerve fibers, to give rise in the brain to 
different sensations of pitch. 

In case of complex vibrations the basilar membrane re- 
solves itself into its elements, one fiber taking up its funda- 
mental tones and other fibers the various harmonies or partial 
tones, the synthesis of the sound as to its quality being 
affected in the nerve cells of the auditory center of the brain. 
While the theory just given is probably the most satisfactory, 
there are others which deserve consideration. One of the 
most important of these is the one which considers that sound 
waves on passing into the endolymph of the cochlear canal 
impress the membrana tectoria, and thus set in vibration the 
hair of the hair cells. 

By those who hold the first theory given, the membrana 
tectoria is considered as a damper to check vibrations, the 
auditory hair serving to convey the damping action to the 
hair cells when excited in some other way. It is also prob- 
able that the organ of Corti has also the power to appreciate 
loudness as well as pitch and quality of tones. As noise has 
the properties of pitch and intensity, the sensory epithelium 
can also appreciate noise as well as musical tones. 

As the sensory epithelium of the cochlea takes note of 
the intensity of pitch and quality of sound, it would seem 
that the sensory epithelium of the vestibular division of the 
nerve must have some other function than the perception of 
sound. It was formerly thought that semicircular canals 
were to aid us in determining the direction of a sound. But 
we have many reasons for not believing this to be their func- 
tion. Their function is probably that of the sense of orien- 
tation, which enables us to determine our position in space, 
and, in connection with the sensation from the skin, muscles, 
and eyes, furnishes help in guiding in the complex co-or- 
dinate movements by which the body is balanced and equi- 
librium is maintained. The varying pressure of the fluid 
endolymph in the semicircular canals gives rise to impulses 



HOW WE HEAR. 437 

in the vestibular nerve endings of the ampullse of these canals 
{scalm aciisficw), producing sensations that enable us to 
become aware of the position of the body. 

It will be noticed that the planes of the three canals lie 
in three axes of the spaces; a movement of the body or a 
change of the position of the head may lead to changes of 
pressure or movements of the endolymph that affect the am- 
pullae differently, and thus give rise to different impulses 
in the vestibular branch of the auditory nerve fibers dis- 
tributed to the ampullse. This theory would seem to be sup- 
ported by the fact that injury to the membranous canals in 
birds and rabbits does not affect the hearing, but produces, 
especially in birds, some loss of co-ordination of movement 
with movement of the head in the plane of the injured canal 
and movement of the eyeballs. 

Another evidence for this theory is that Meniere's dis- 
ease, the chief symptoms of which are giddiness and stagger- 
ing, has been found to be associated with affection of the semi- 
circular canals. 

By some the sensory epithelium of the maculae in the 
utricle and saccule has also been considered as connected with 
the sense of movement, and to have no connection with hear- 
ing. But there is doubt as to the truth of this statement, as 
there are animals low in the scale of organization that have a 
vestibular labyrinth without a cochlea, or with but a trace 
of one, that without doubt hear distinctly. In some crus- 
taceans the organ of hearing is a mere spherical vesicle, 
partly lined by auditory hair cells, and some of these have 
been seen vibrating to sounds, the otoliths being forced down 
on the vibrating hairs to act as a damper when the sound 
was intense. It is not known, however, whether the vestibular 
nerve filaments of the utricles and saccule have the power 
to distinguish anything more than intensity. The fact is that 
the whole mechanism of hearing is far from being satisfac- 
torily settled. 

When the sensation of sound is produced in the mind, 
certain judgments respecting it form its conclusions by 



438 HEARING. 

knowledge previously acquired and by the aid of the other 
senses. Like visual sensations, which are referred not to the 
retina but to external objects, so the ear refers sound not to 
itself, but to something outside of the ear. 

When the meatus (auditorius) is filled with water, the 
idea of the externality of the sound to the body disappears, 
and the sound that then reaches the tympanic membrane 
seems to originate in the head. The direction of sound is 
probably determined chiefly by the difference of intensity 
with which it is heard by each ear. 

If the sound is directly behind, before us, or directly 
overhead, we are in doubt as to its direction until we turn the 
head to one side or the other. The determining of the dis- 
tance from which a sound comes is largely an acquired per- 
ception, depending on previous experience of the quality of 
sound at various distances. 

Anything, however, which prevents the sound varying 
normally (inversely as the square of the distance), as when 
the sound comes through a speaking tube, deceives us as to 
the direction, and causes us to judge of its being much 
nearer. The ventriloquist deceives by imitating the char- 
acter of a distant sound; we thus judge it as far away, it 
being, however, near. 

The slight difference between the intensity of the im- 
pression on the two ears does not give rise to the idea of two 
sounds, but we hear them as one, for they are in some way 
fused. The biaural audition in the normal mode of hear- 
ing aids us in our perception of space, but not in so high a 
degree as binocular vision. 



CHAPTER XX. 

THE VOICE. 
EXPERIMENTS AXD DEMONSTRATIONS* 

Dissection of the Larynx. — Obtain from the butcher the 
larynx (Fig. 171) of a sheep or ox. It usually has the 
esophagus attached, and surrounded by a mass of muscle and 
connective tissue. 

1. Slit the esophagus lengthwise, and turn it back so as to 
observe the opening (the glottis). Xotice the lid-like car- 
tilage (the epiglottis) which bounds it in front and at the 
sides by folds of the mucous membrane, and behind by the 
large converging yellow crests of the arytenoid cartilage. 
Xotice that the mucous membrane of the larynx is continuous 
with that of the esophagus. 

2. Cut away the esophagus, being careful not to cut the 
muscles of the larynx. Xotice the prominent projection 
{Adams apple) on the front part of the larynx. Trim away 
the muscles and other tissues from the front part of the 
larynx. Xotice the cartilage (the thyroid cartilage) which 
forms the greater part of the larynx. Xotice the relation of 
the muscles of the larynx to those of the esophagus. Xotice 
the relation of the thyroid to the bone (Jiyoid hone) and the 
membrane (thyro-hyoid) which connects them. 

3. Examine more carefully the nature and relation of 
the epiglottis. It is elastic. Press it down to see how it 
covers the glottis. What position does it take when released ? 
Xotice the muscle back of the upper angle of the thyroid car- 
tilage and attached to the base of the epiglottis. Determine 
its function by pulling on it, and notice the effect produced by 
its shortening. 

4. Xotice the ring of cartilage (cricoid cartilage) below 
the thyroid marking. How do its anterior and posterior 
surfaces differ ? How is it connected to the thyroid cartilage ? 
Is the membrane muscular? In case of movement of these 
cartilages, where are their fixed points ? 

439 



440 THE VOICE. 

5. Notice the two curved yellowish cartilages (the aryte- 
noid cartilages) projecting upward and backward from the 
top of the larynx. Are they movable ? What relation do 
they bear to the cricoid cartilage? Determine what effect 
this movement backward and forward has upon the project- 
ing ridges {vocal cords) which meet back of Adam's apple. 

6. Examine the muscles which move the arytenoid car- 
tilages: (a) One on each side of the posterior surface, the 
cricoid, which passes upward and is attached to the arytenoid 
of the same side. What effect would its contraction have on 
the arytenoid, and through the arytenoid on the vocal cords ? 
Determine by dissecting it loose from the cricoid and pulling 
on the muscle. (b) The muscle (lateral crico-arytenoid 
muscle) arising from the upper edge of the lateral portion of 
the cricoid and passing upward and backward to the aryte- 
noid. Determine its action by cutting it loose from its origin 
on the cricoid, (c) The broad muscle (thyro-arytenoid mus- 
cle ) which arises along the whole length of the angle of the 
thyroid and joins to the arytenoid by converging fibers. By 
cutting it loose from below determine its action, (d) The 
muscle (arytenoid muscle) on the posterior surface of the 
arytenoid. What is its action? 

7. Remove one of the arytenoid cartilages from its con- 
nection with the cricoid. How is it attached ? How do you 
account for the synovia found at their articulation? Re- 
move the muscle and other tissue so that you can study its 
shape more fully. 

8. Remove the upper cartilage so as to expose the interior 
of the larynx. 

9. Determine the interior of the larynx by cutting a 
specimen on the median line on the anterior surface. Ex- 
amine another specimen from its anterior surface. How 
do the vocal cords seem to be formed ? 

10. Examine the larynx of some member of the class by 
means of a hand mirror or a laryngoscope. How do the posi- 
tion of the cords differ in high and low notes ? What is their 
condition in breathing ? 

THE VOICE. TEXT. 

The Organ of Voice. — Speech is one of the crowning fea- 
tures which distinguishes man from the other animals, and 
gives him pre-eminence over all created existences. 



THE ORGAN OF SPEECH. 441 

The chief organ of this wonderful power is the larynx, 
which is situated at the upper and fore part of the neck 
between the large vessels of the neck, below the tongue and 
hyoid bone, and in front of the esophagus. It is composed 
of cartilage arranged into a funnel-shaped framework con- 
nected by elastic membranes or ligaments, two of which pro- 
ject into the cavity forming the vocal cords, these being more 
intimately connected with the production of the voice. The 
different cartilages are connected also by muscles, and have 
the power of movement one upon the other, and thus modify 
the form of the larynx and the tension of its ligaments. Its 
mucous membrane is continuous with that of the pharynx 
and with the trachea below. 

Structure of the Larynx. — The larynx is composed of 
nine cartilages, three single ones and three pairs: Thyroid, 
cricoid, epiglottis, two arytenoid, two cornicula larynges, two 
cuneiform. 

The cornicula larynges and the cuneiform cartilages are 
very small. The large shield-shaped cartilage in form and 
at the sides is the thyroid. The ring-shaped cartilage below 
is the cricoid. The leaf-shaped cartilage above the opening 
(glottis) to the larynx, the epiglottis, and the hooked-shaped 
cartilage surmounting the cricoid, is the arytenoid. Care- 
fully study Fig. 171. 

The epiglottis is a plate of yellow fibro-cartilage, being 
attached by its narrow part to the interior of the thyroid 
cartilage at the front. It takes little or no part in the pro- 
duction of the voice. In swallowing it falls downward and 
backward, closing the glottis ; at other times it stands upward, 
giving a free entrance to the larynx during respiration. 

The thyroid (Fig. 172) is formed of two lateral halves, 
or wings, opened behind, but forming a ridge at an acute 
angle in front, the prominent point of which forms Adam's 
apple (pomum A da mi). 

Its sides, or wings (alee), are quadrilateral in form, and 
have attached to their outer surface the star no-thyroid and 
thyro-hyoid muscles. As we have said, the epiglottis is 



442 THE VOICE. 

attached to the inner surface of the thyroid at the angle and 
below the true and false vocal cords and thyro-arytenoid 
muscle. A membrane (thyro-hyoid) unites the upper edge 
of the thyroid to the hyoid bone, and it has below a mem- 
brane (crico-thyroid) connecting it in the front and on the 
sides by means of muscle (crico-thyroid muscle) to the cri- 
coid cartilage. The posterior edge of the thyroid ends above 
and below in a prominent projection, or cornua, the inferior 
one articulating with the lateral surface of the cricoid car- 
tilage. 

The cricoid cartilage is situated below the thyroid, with 
its broadest part lying behind in the gap between the alse of 
the thyroid and its narrow part in front, and joined to the 
thyroid by a membrane (crico-thyroid). By its lower border 
it is attached to the front ring of the trachea; its upper 
border at the highest part has on each side a smooth oval 
surface for articulation with the arytenoid cartilages. 

The arytenoid cartilages resemble an irregular three- 
sided pyramid, and rest by their bases on the posterior and 
highest part of the cricoid cartilage, their apices turning 
backward and inward, and at their extremities surmounted 
by the two small cartilaginous nodules (cornicula larynges). 
From the anterior angles of the arytenoid the true vocal 
cords pass, to be attached in front to the thyroid in the angle 
between the lateral ahe (Fig. 171). 

The true vocal cords are situated below the false vocal 
cords, and consist of two folds of mucous membrane inclos- 
ing and supported by fibrous tissue. The passages between 
the false vocal cords and the true cords are known as the 
ventricles of the larynx (Fig. 173), which leads into the ves- 
sels between the false vocal cords and the thyroid cartilages, 
called the pouches of the larynx (Fig. 173). 

The opening between the true vocal cords is called the 
glottis or rima glottis. It passes horizontally from the ary- 
tenoid cartilage behind to the angle of the thyroid in front, 
in the male being less than an inch in length and more than 
a third of an inch when dilated. Its form, however, varies, 



THE ORGAN OP SPEECH. 443 

being widely open and somewhat triangular in quiet breath- 
ings but in the production of different tones of the voice the 
fissures become narrowed, the inner margins of the arytenoid 
cartilages meet, and the free edges of the vocal cords approx- 
imate and become parallel, varying in their nearness and ten- 
sion with the pitch of the tone produced (Fig. 174). 

The muscles of the larynx may be learned by study of 
Plate XVIII. 

The nerve supply of the larynx is derived from the supe- 
rior laryngeal and inferior laryngeal branches of the vagus, 
the superior supplying the mucous membrane and crico-thy- 
roid muscles of the larynx. 

Voice and Speech The sounds of the human voice are 

produced by blasts of air, which set in vibration the true vocal 
cords. 

The glottis during ordinary respiration is about half 
open, and widens slightly with each inspiration; with forced 
inspiration it becomes widely dilated, but, when vocaliza- 
tion takes place and the cords are set in vibration, the glottis 
becomes a mere chink with parallel sides. 

By voice we mean the sound produced in the larynx by 
an expiration blast of air, setting in vibration the vocal cords. 
To produce voice the chink of the glottis must be narrowed 
by the free edges, and more or less nearly parallel, and the 
cords put on a more or less tension, the tension and approach 
of the cords being regulated by muscles, as shown in table, 
page 56. The loudness of the voice depends largely on the 
force of the expiratory blast affecting the tension of the 
cords. 

In different voices the pitch depends upon (1) the length 
of the cords, varying as the length of the cord, the lower 
tones being produced by the long cords and the higher ones 
by the shorter cords. In women the vocal cords are one 
third shorter than in men, hence their voices are of a 
higher pitch. In most cases tenor singers have shorter cords 
than basses; sopranos, than contraltos. The change in the 
voice of males is due to the enlargement of the larynx and 



444 THE VOICE. 

the lengthening of the vocal cords, hence the deeper tones. 
The age at which the voice changes varies in different indi- 
viduals, ranging from fifteen to nineteen years. (2) With 
the tension of the cords, the tighter the cords, the higher the 
pitch. Tones of various pitch may be produced by varying 
the tension of the vocal cords, as the muscles are brought 
under the control of the will. What is known as falsetto 
tones are thought to be produced either by the vibration of 
the edges of the cords only, or by the vibrating portion of 
the cords being shortened. The chest tones are produced by 
the vibration of the cords being communicated to the column 
of air in the resonant tubes above the larynx and in the 
trachea below. 

Tones may have the same pitch, but differ very much in 
their quality. The property of a tone which enables us to 
distinguish it is known as quality or timbre. You may 
sound tones of the same pitch on a violin, piano, and flute, 
yet you easily recognize the tones of the different instru- 
ments ; this is due to their timbre. We recognize the voices 
of our friends by their timbre. 

Timbre depends principally upon overtones or harmonies 
which are produced at the same time as the fundamental. 
Thus when a bell is struck, the sound breaks up into portions 
or segments, one producing the fundamental, and the others 
the overtones, thus modifying the fundamental, giving as a 
result a complex tone and the characteristic tone or quality. 

The quality may be due (1) to the nature of the vibrating 
substance; (2) to the overtones; (3) to the nature of the 
resonant body. 

A voice sound seems to be very simple, yet, in reality, it 
is very complex, being made up of a fundamental tone and 
a number of accessory tones or harmonies, so that the audible 
tone produced in the larynx may be so affected in its passage 
through the adjustable resonant cavities and mouth, as to 
become speech. The quality of different voices is due to the 
different set of overtones that predominates ; these being de- 
termined not only by the length and physical condition of 



HOW WE SPEAK. 445 

the cords, but also by the structure aud form of the throat, 
mouth, aud nasal passages. 

Speech. — Speech is voice modified by alternations and 
additions made in the pharynx, mouth, and nose. The organs 
producing these modifications are called organs of speech. 
The teeth, tongue, and lips are called the organs of articula- 
tion. The sounds formed in the larynx are communicated 
to the air, and undergo modifications from the varying size 
of the cavities above and by the varying position of the tongue 
and lips, transforming the laryngeal sounds to articulate 
speech, consisting of syllables joined to form words. Speech 
may be produced without voice, as in whispering, where the 
sounds are produced in the mouth alone. The various sounds 
produced in speech are called elementary sounds, which are 
divided into vowels with consonants. 

The vowels are the more open continuous tones. They 
differ only in the quality given to the tone by the overtones ; 
they are re-enforced and modified in the cavity of the mouth 
and nasal passages, and they may all have the same pitch. 
The greatest modification is produced by the change in the 
form of the mouth. Plelmholtz, by means of resonators, made 
an analysis of the vowels into their component vibration. He 
also succeeded in reproducing them synthetically. 

Also note the form of the mouth and the position of the 
posterior part of the tongue in giving the vowels. Verify 
the following: (1) that in the production of the broad sound 
of a, as in far, the mouth is somewhat funnel shaped, with 
the wide part outward; (2) for o, as in more, it is like a 
little bottle with a Avide neck; (3) for o, as in poor, the vocal 
chamber is large, with a narrow opening at the mouth ; (4) 
for e and i, when having the sound of eh and ee, the mouth 
has the form of a bottle with a long and narrow neck, formed 
by raising the tongue toward the hard palate. 

Diphthongs are produced by the mouth changing its form, 
as it would in passing from one vowel to the other. 

The closer and less continuable sounds of speech are called 
consonants, and it should be borne in mind that there is no 



446 THE VOICE. 

sharp line of distinction between vowels and consonants, some 
of the most open consonants sometimes having the value of 
vowels. 

Most of the consonants are produced by irregular vibra- 
tion, having more of breath and less of tone than vowels, 
more like noise, less musical. In their production there is a 
narrowing of some part of the pharynx or mouth, which 
interrupts and modifies the air vibration from the larynx, 
or sets up other vibrations in particular parts. The conso- 
nants are divided, (1) as to the producing parts into labials, 
or lip letters, p, ~b, v, m; dentals, teeth letters, t, d, th; gut- 
turals, or throat letters, which are made up at the top of the 
throat with the back of the tongue, g; (2) as to the degree 
of closeness or the mode of their production; into mutes, ~b, p, 
in which there is a complete shutting off the passages of the 
breath ; aspirates, as th, f, v, s, z, in which there is a friction 
of the breath through the nearly closed passages ; nasal, as n, 
m, ng, the breath being admitted through the nasal passages, 
and thus acquiring a peculiar resonance. 

Stammering is produced by an irregular and spasmodic 
contraction of the diaphragm by which the expiratory bases 
of air upon which speech depends is interfered with. In 
some persons mental disturbance will produce stammering. 

An inability to manage the larynx and other parts so as 
to form words produces stuttering. 



APPENDIX, 



I. HISTOLOGICAL METHODS AND REAGENTS. 

Steps in the Preparation of a Permanent Mount. — In pre- 
paring a tissue for a permanent mount, the following steps 
are usually required : — 

1. Killing. — By this is meant the destroying of the 
life of the tissue, which should be immediate, as gradual 
killing may bring about changes which modify very much 
the structure of the tissue. 

2. Fixing. — This is so treating the tissue that its his- 
tological structure will be preserved, and decomposition will 
be prevented. 

3. Staining. — The purpose of staining is to color the 
tissue so as to bring out more clearly its structure. Many 
tissues are so transparent that, without coloring, they appear 
structureless. The different parts of the tissue stain differ- 
ently, and thus are more easily distinguished and studied. 

\. Hardening. — Many of the tissues have to be cut into 
very thin sections in order to be studied to advantage ; and 
to give the tissue firmness so that sections can be made, they 
are treated with reagents to harden them. 

5. Imbedding. — The tissues which, after hardening, are 
not firm enough to be cut, are impregnated with a substance 
which makes them firm enough for section cutting. 

6. Section Cutting. — This is usually done by means of 
an instrument called a microtome, by which the specimen is 
cut into very thin sections. 

7. Mounting. — The sections are so treated that they can 
be put in dammar on the glass slip, and covered by a glass 
circle, and preserved. 

The time required for these different processes and the 
reagents used will depend on the tissue. For most tissues 
the following will give good results : — 

Killing and Fixing. — Three grades of alcohol, 60, 70, 
and 80 per cent respectively. Keep in 60-per-cent alcohol 
from 2 to 6 hours; in 70-per-cent, 3 to 8 hours; and in 80- 

447 



448 APPENDIX. 

per-cent, 6 to 48 hours. The pieces of tissue, as a rule, should 
not be over three eighths of an inch on a side. When, how- 
ever, this size does not include the size of the entire section 
of the part desired, — as that of the spinal cord, esophagus, 
or trachea, — the entire cross-section may be used ; but it 
should be made thin — not over one eighth of an inch. When 
the tissue has become firm, it is ready for staining. 

Staining. — Eemove from the 80-per-cent alcohol to a 
solution of picro carmine for 2 to 48 hours. The solution 
should be from eight to ten times the volume of the pieces 
to be stained, and put in a convenient-sized vessel. One- 
ounce slat-mouthed bottles are very convenient for holding 
staining and hardening solutions. The pieces should be re- 
moved from the staining solution as soon as they are colored 
through, which may be told by making a section of one of 
the pieces. 

Hardening. — When thoroughly stained, remove the pieces 
from the staining solution, and place in 80-per-cent alcohol 
from 2 to 6 hours. This will remove the excess of stain. 
When the tissue becomes firm, remove the pieces to 95-per- 
cent alcohol, in which they should remain until quite firm 
(10 to 20 hours) ; then place for 15 hours or more in abso- 
lute alcohol, which removes all the water from the tissue. 

Imbedding. — The object of imbedding is to filtrate the 
tissue with a substance which, when cold, will give to the 
tissue firmness, so that section may be made. The best ma- 
terial for most tissues is paraffin. Paraffin will not enter a 
tissue containing water, hence the importance of complete 
dehydration, as given under hardening. Paraffin is not sol- 
uble in alcohol : the alcohol must be removed by placing the 
pieces, when thoroughly hardened, in spirits of turpentine 
from 2 to 8 hours. If the pieces become very hard, or appear 
shrunken, they should be removed at once. As soon as the 
specimen becomes firm under pressure of the scalpel, remove 
to a saturated solution of paraffin and spirits of turpentine. 
To make the solution of paraffin, add to one ounce of spirits 
of turpentine heated to 45° to 60° C, small pieces of paraffin 
as long as it readily dissolves. When the solution is com- 
plete, remove the pieces from the spirits of turpentine, and 
put them in the paraffin solution, in which they should re- 
main from 2 to 4 hours. The paraffin solution can be kept at 
the desired temperature by means of a water bath. Regulate 



HISTOLOGICAL METHODS. 449 

the flame of the burner so as to keep the temperature uni- 
form. Melt the paraffin in a shallow vessel, and keep it one 
or two degrees above its melting point. Remove the pieces 
from the paraffin solution, and put them in the melted par- 
affin, in which they should remain from 2 to 4 hours. 

Make two L-shaped pieces of lead one-half inch on cross- 
section, and one inch long by three fourths of an inch wide. 
Place the L-shaped pieces on a glass slip (2x2 in.), so that 
they will inclose a space three fourths of an inch square. 
Pour some of the melted paraffin into the space, and as 
quickly as possible remove one of the pieces from the bath, 
and put it in the melted paraffin of the molds. The pieces 
may be handled by means of forceps, which should be kept 
warm by keeping them, when not in use, on the water-bath. 
Put the glass slip and molds into cold water, so that the 
molds will be almost covered by the water, and as soon as 
the upper surface of the paraffin becomes hard, let the glass 
slip and molds drop into the water so as to immerse them. 
Leave them in the water until the paraffin is hardened. Re- 
move from the water, and strike the edge of the slip against 
the table, which will release the molds. Remove the mold 
from the block of paraffin. 

Section Cutting. — Cut off the end of the section, being 
careful to cut off only a very thin portion of the tissue im- 
bedded. If the tissue is soft, it will not cut well ; it should 
be firm, and show no signs of moisture. The paraffin block 
may be made to adhere by warming the receiver of the block, 
and gently pressing the end of the block against it, and then 
cool. Before cutting sections, the imbedding material should 
be cut away as much as possible from around the tissue, as 
it is easier to cut sections when the surface to cut is small 
than when it is large. The razor should be very sharp. Put 
under the microtome knife or razor a piece of paper to catch 
the sections as they are cut. 

Mounting the Sections. — Clean thoroughly a glass slip. 
Place on the center of the slip, by means of a earner s-hair 
brush, a very thin film of a solution of collodion and clove oil 
(three parts collodion to one part of clove oil). Make the 
film as thin as possible. At once place on the film one of 
the thin sections. Gently heat over the alcohol flame until the 
paraffin is melted, and then immerse the section in a glass 
of spirits of turpentine. Leave in the turpentine until the 
29 



450 APPENDIX. 

paraffin is dissolved. If the section is opaque on drying, it 
should be put back into turpentine, as the paraffin has not all 
been dissolved out. When the paraffin has all been dissolved, 
the section will be transparent. Wipe off the turpentine from 
around the section, and place on the section a drop of dam- 
mar or Canada balsam; clean thoroughly a glass circle or 
square, and put it on the drop of dammar. Press gently the 
cover to secure the spreading of the dammar. Place the 
slide away in a tray so that it will rest flatwise. Keep in the 
trays until the dammar is dry. 

Other Methods. — Use of Chloroform. — Place the tissue 
to be imbedded in chloroform containing enough ether to 
keep the tissue from floating. Warm the tissue and chloro- 
form to the melting point of the paraffin used, small pieces of 
paraffin being added during the warming. When bubbles 
are no longer given off from the object, the paraffin has dis- 
placed the chloroform, and the specimen is ready for imbed- 
ding by the same method as used for the turpentine. For 
nerve tissue, in embryological specimens, the chloroform 
method of infiltration is the best. 

Staining on the Slide. — In this method the specimen is 
killed, fixed, and dehydrated as in the method given, the 
only difference being that it is not placed in the staining solu- 
tion. It can be imbedded by either of the methods given, 
and sections made. Proceed as given above for mounting, 
except when the paraffin is dissolved out, wipe off as 
much of the turpentine as possible, and then add a few 
drops of alcohol, after which add a few drops of the staining 
solution. Let the staining solution remain on the section 
for ten or fifteen minutes, or until the section is well colored. 
Remove most of the staining solution by means of blotting 
paper, placed at the edges of the object ; dehydrate by adding 
absolute alcohol. Remove excess of alcohol by means of blot- 
ting paper. Add a few drops of turpentine to remove the 
alcohol. Remove the excess of turpentine by means of blot- 
ting paper, then add a drop of dammar or Canada balsam, 
and put on cover glass. 

Other Stains. — Ilcematoxylin is a better stain for nerve 
tissues than picrocarmine, and may be used as directed for 
the latter stain. If sections are stained too deep, the excess 
of stain may be removed by treatment with dilute hydro- 
chloric acid until proper depth of stain is secured. 



HISTOLOGICAL METHODS. 451 

Methylene blue is of especial value as a stain for lym- 
phoid tissues, lymphatic glands, and nerve tissues. 

Examination of Blood. — Prepare slide as directed on 
page 167, Experiment 1 ; then treat the blood film with two 
or three drops of Chenzynky's solution, and let the solution 
dry. When dry, remove excess of stain by treating with 
two or three applications of alcohol. Add the alcohol by 
means of a pipette, and after one or two minutes, remove 
the alcohol with blotting paper. Repeat this treatment two 
or three times. Let the slide dry, then warm the slide to 
soften the ring of Brunswick black, and softly put on the 
cover glass. By this stain the red corpuscles will be colored 
red and the leucocytes, blue. 

Biondi's Method. — "A drop or two of blood is mixed with 
5 c.c. of osmic acid solution (as a rule it should be strong, 1 
to 2 per cent), and allowed to remain in it from one to twen- 
ty-four hours/' — Lee. Put a drop of solution on glass slip, 
let it dry, and color with picrocarmine. 

Staining Micro-organisms. — Koch's Method for Bacteria 
in Tissues. — " Stain in aqueous solution of methyl violet, 
fuschin, or methyl-blue. Wash in a saturated solution of 
potassium carbonate diluted with an equal volume of water. 
The color will be removed from the nuclei of the cells, but 
remains in the bacteria; dehydrate, clear in cedar oil, and 
mount in balsam." — Gould. 

Bacillus Tuberculosis. — Clean five or six cover glasses. 
Hold with the forceps each cover glass in the sputum so as to 
get a thin film on one surface of the glass ; place on a clean 
glass square, so sputum side of cover glass will be up ; cover 
with bell-jar, and let stand until dry. When dry, hold the 
glass covers in Gibbe's double stain for bacillus so as to have 
sputum side down and in the stain. Replace the cover 
glasses to the glass square, and let them dry as before. When 
dry, wash cover glasses in alcohol to remove the excess of 
stain and to dehydrate; let cover glass dry, and mount in 
balsam. Bacillus tuberculosis will be colored red; other 
bacilli, as well as the microcci, blue. 

Examination of Bone. — (1) 'Without Decalcification. — 
With a bone saw make as thin a section as possible ; glue the 
section to one end of a cork, and file the section as thin as 
possible ; smooth the section on a fine-grain hone-stone. Soak 
off the section from the cork by heating it in hot water ; glue 



452 APPENDIX. 

the smooth side to the cork, and work down the rough side 
with the file and hone, making the section as thin as possible 
and of uniform thickness. Mount as directed on page 166, 
!No. 34. Sections of teeth may be made in the same way. 
(2) Decalcified Bone. — Treat a small section of fresh bone 
with 95-per-cent alcohol for one or two hours, after which 
place the section into a ten-per-cent solution of nitric acid, 
which should be changed daily for eight or ten days. The 
section should be removed as soon as it is decalcified, as the- 
acid will stain it yellow if left too long, or after the decal- 
cification is complete. Remove the section, and wash for one 
or two hours in running water, and then place in 95-per-cent 
alcohol, in which it should be kept for a few days, when the 
alcohol should be changed. When dehydrated, section may be 
made, stained for five or ten minutes in a weak aqueous solu- 
tion of eosin. " The ground substance and small cells of car- 
tilage remain colorless; the nuclei of the large cells are 
stained red, and so is the periosteum, bone-tissue, and cellu- 
lar contents of medullary spaces." Dehydrate section in 
absolute alcohol, and mount in benzol solution of Canada 
balsam. Busch's method, Lee's Microtomist's Vade-Mecum. 

Warming the Slide. — In examining many live speci- 
mens, as the white corpuscles, it is necessary to keep the slide 
warm during the examination ; this may be done by means of 
a triangular piece of sheet iron. The piece should be six 
inches long and one and a fourth inches wide at its widest 
portion. In the larger end there should be a hole three 
fourths of an inch in diameter.. To warm the slide, place the 
larger end of the triangular piece so that the hole will be 
over the opening of the stage of the microscope. Put over 
this the slide to be examined, and clamp the slide down so 
as to hold the pieces in place, and place under the tapering 
end the flame of an alcohol lamp or Bunsen burner. If only 
a slight temperature is needed, put only the tip of the piece 
in the flame ; if more heat is needed, bring the flame nearer 
the microscope. 

To Clean Cover Glasses and Slides. — Leave cover glasses 
in dilute nitric acid for one hour or more, after which wash 
thoroughly in water, and let the glasses dry, where they will 
be free from dust. When they are dry, treat with benzole 
(benzene) or wood spirits (methyl alcohol). To remove bal- 
sam or dammar from slides, let them stay in spirits of tur- 



BACTERIOLOGY. 453 

pentine several hours, and then thoroughly wash in spirits 
of turpentine. 

To Remove Covers from Balsam and Dammar Mounts. 
— Soak the mounts in spirits of turpentine for several days, 
until the dammar or balsam is softened, when the cover 
glasses may be removed by pushing the covers sidewise until 
they are removed from the slide. The covers and slides may 
then be cleaned as directed in the paragraph above. 

Synthol. — This is a perfect substitute for alcohol, and 
may be used for all the purposes for which alcohol is used, 
except internal consumption. The author has given it a 
thorough test, and found it to be all that is claimed for it. 
It is equal to alcohol as killing, fixing, or hardening agent, 
and may be substituted for alcohol for making stains, re- 
agents, etc. It has an advantage over formaldehyde, as it 
does not affect the eyes as the latter substance does. "As a 
preservative it is superior to any alcohol." 

The author recommends its substitution for alcohol in 
the various experiments where alcohol is used. 

Formaldehyde.. — This is a good fixing and preserving 
agent. Tissues desired for examination can be preserved 
in it, and kept until needed for examination. If the speci- 
mens are to be handled with the hands, the specimens should 
first be washed in several changes of water. The pungent 
odor of formaldehyde may be counteracted by a few drops 
of ammonia. 

BACTERIOLOGY. 

Separation and Isolation of Bacteria. — When bacteria 
occur together, it is sometimes quite difficult to recognize 
them, even under high power. One of the first steps in the 
propagation of bacilli is isolation. This is done by using 
cultures, by means of which a particular species of bacillus 
is separated from other species, and its multiplication is 
favored. By this means they form into colonies, which 
may in most cases have a characteristic form or coloring by 
which they may be recognized even by the unaided eye. The 
identification thus becomes easy and certain. The bacilli 
may be separated by means of a platinum wire (ISTo. 30), 
which is first sterilized by holding it in a Bunsen flame for 
a short time. Sterilize a test tube, and place in it 5 c.c. 



454 APPENDIX. 

of a sterilized culture medium. The tube may be sterilized 
by heating it to 20° C. in the air oven for fifteen or twenty 
minutes. To separate the bacilli, dip the platinum wire 
into the fluid containing the bacilli, and then place the wire 
into the culture. Plug the end of the tube with cotton that 
has been sterilized by heating it almost to the point of 
scorching. If the laboratory is not provided with a special 
apparatus for cultures, they may be kept at the proper tem- 
perature by means of a water bath or an incubator. The 
temperature required will vary with different bacilli. The 
culture should be carefully watched, and the changes care- 
fully noted. 

Kinds of Media Used for Culture. — The media used for 
culture are of two kinds, (1) liquid and (2) solid. 

Liquid Media. — Until recent years the liquid media were 
exclusively used. The more important liquids used are, 
broth made from various meats, infusions of various vege- 
tables, malts, solutions of yeast, solutions of various salts, 
with suitable proportions of sugar, peptone, or other organic 
substance added to give nutritive value to media. 

Solid Media. — The more common solid media are slices 
of potato, hard-boiled egg, and broth, to which enough gel- 
atin or agar-agar has been added to make the media solid 
at the temperature of the culture. In some cultures, like 
that of B. tuberculosis, solid blood serum is used. The more 
important advantages of solid media are, (1) that the organ- 
isms introduced into them are confined to the spot where they 
are placed, and around this spot the colony forms, not infect- 
ing the entire medium, as is the case with liquid media ; (2) 
the obtaining pure cultures by Koch's method of plate cul- 
ture. This method consists in taking a portion of the sub- 
stance containing the micro-organisms, and thoroughly mix- 
ing them with some melted gelatin or agar-agar medium in a 
test tube, then pouring this mixture out on a horizontal plate, 
which on cooling forms a thin film on the plate. The plate is 
put in a moist place, and kept at the proper temperature, 
and in the course of a few days each organism introduced 
into the culture will have given rise to a separate and isolated 
colony, visible to the naked eye, and often presenting a very 
characteristic appearance when examined with a low power. 
Each of these colonies will be a pure culture, and fresh cul- 
tures may be made from them by inoculating new media. 



BACTERIOLOGY. 455 

This method presents the following advantages: (1) "It 
enables ns to procure pure culture; (2) to test cultures sup- 
posed to be pure; (3) to ascertain the actual number of 
organisms present in a given quantity of substance; (4) to 
identify or differentiate between organisms, through the char- 
acteristic appearance of their colonies.'' 

A Good Culture Medium. — Nutrient gelatin, most use- 
ful for the growth of all kinds of bacteria, is prepared in 
this way : — 

" One pound of lean beef is cut up, to it is added one pint 
of water, and the whole kept boiling in the digester or any 
other vessel for from half to three quarters of an hour. After 
having been strained through fine calico, it is filtered through 
paper into a beaker. Bring up by adding water to 600 c.c. ; 
add to this 60 grams of the finest gold-label gelatin, cut up 
in small pieces, 6 grams of peptone, and 6 grams of common 
salt. Dissolve in a water bath, but do not let the water 
boil; neutralize with carbonate of soda or, better, with 
liquor potassgp, till faintly alkaline; boil for half an hour, 
run through a hot filter into a sterile flask plugged with 
sterile cotton wool, and bring it up to boiling point, at which 
it is kept for a few minutes. This can be kept as a stock 
gelatin." — Klein, "Micro-Organisms and Disease/' 

Examination of Bacteria. — Place into each of several 
sterilized test tubes about 5 c.c. of the stock solution of gel- 
atin, and make the following test : — 

1. One tube unexposed to micro-organism and kept 
plugged with sterilized cotton. 

2. One tube exposed to the atmosphere, and kept un- 
plugged. 

3. One tube exposed to the water from the hydrant, and 
after exposure kept plugged with sterilized cotton. 

-i. One tube exposed by placing in it a small amount of 
dust, and after exposure kept plugged with sterilized cotton. 

5. One tube exposed to some milk, then plugged with ster- 
ilized cotton. 

6. One tube exposed to pond water, or to an infusion of 
hay. 

Label the tubes, place in a moist place, and keep them 
at a temperature of about 20° or 25° C. 

Examine from time to time, and carefully note the 
changes. 



456 APPENDIX. 

In a similar way test other substances, as the secretions 
of the mouth, the material between the teeth, spoiled fruit, 
etc., the sputum of a healthy person, the sputum of a con- 
sumptive, and other material you may be able to secure. 

Conditions Necessary for the Growth of Bacteria. — Pro- 
cure some good culture, inoculate a number of tubes of media, 
and place them under different conditions of moisture, tem- 
perature, degrees of alkalinity and acidity, different degrees 
of saltness, with and without spices, with and without air. 

Make a list of the favorable conditions, also those that 
are unfavorable, and those that destroy bacteria. How would 
you sterilize milk, water, fruits ? 

Cautions to be Observed in Handling Bacteria. — In han- 
dling pathogenic bacteria material, the greatest care should 
be exercised. Carefully observe the following: — 

1. Do not handle the material with the bare hand, and 
sterilize all instruments immediately after use by leaving 
them for a few minutes in boiling water, or in a 30-per-cent 
solution of carbolic acid, or a .01-per-cent solution of cor- 
rosive sublimate for one hour. Never use formalin with 
steel or iron instruments. Never lay an instrument on the 
table after it has been contaminated with the infected 
material. 

2. Be sure that there are no wounds or sores on the 
hands, and be careful not to wound the hands with instru- 
ments used. 

3. After inoculating a culture, immediately sterilize the 
platinum wire used by holding it in a Bunsen flame for a 
short time. Never lay down the platinum wire without first 
sterilizing it. 

4. After the inoculation of the cultures, destroy all in- 
fected material, either by burning or by thorough disinfec- 
tion with corrosive sublimate or formalin. 

5. Thoroughly disinfect all apparatus used. 
Microscopic Examination of Bacteria. — Few if any of 

them can be examined satisfactorily under less than a one- 
twelfth-inch objective, and many of them require special 
staining and a one-twentieth-inch objective; still there are 
those which these powers do not define. 

By means of the platinum loop, a small portion of the 
colony may be removed, placed on a cover glass, the material 
put under a desiccator, and let dry; color as directed with 



THE MICROSCOPE. 457 

methylene blue or any other stain desired, and stain as given 
in general method. If the media contain gelatin, it is best 
to complete the drying by carefully heating over the alcohol 
flame, only letting the flame come to the surface not coated 
with the media. After staining, wash out excess of stain by 
proper solvent (see methods given above). Dry, and mount 
in balsam. Use oil immersion lens. 

When pure cultures have been made, good results may 
be secured with a one-eighth-inch objective dry lens, and in 
many cases with the one-sixth-inch objective ; especially is 
this true of bacteria that have characteristic grouping. 

Special Methods. — (1) For Bacteria in Milk or Fatty 
Substances. — " Dilute the milk with an equal quantity of 
water, or, in case of denser substances, with a larger vol- 
ume. Spread on cover glass, and fix by heating. After it 
has become dry, stain for five minutes in twelve or fifteen 
drops of methyl blue to which three or four drops of chloro- 
form have been added. Then remove, and allow the chloro- 
form to evaporate; wash in water; mount." — Ahrens 
Method. 

(2) Preserving Sputum. — "Let the patient expectorate 
into a receptacle containing 95-per-cent alcohol, in which 
the sputum may remain for several months, and in which it 
is hardened by dehydration and coagulation. A few drops of 
caustic potash solution added to a small lump of the hard- 
ened sputum on a slide will liquify it in a few minutes, and 
from this the cover-glass preparations are made. When 
dry, Rx the film by passing the cover glass thrice through 
the flame of the spirit lamp, wash in water to remove the 
potash, and then stain according to any of the given meth- 
ods." — SavelieWs Method. 

THE MICEOSCOPE. 

The Simple Microscope. — Of the various forms of the 
simple microscope the Barnes Dissecting Microscope is the 
most convenient, as well as one of the cheapest. For teasing 
specimens and for examination requiring low power, this 
instrument should be used. 

The Compound Microscope. — The parts of a compound 
microscope may be learned by a careful study of Fig. 175. 

The Objectives. — For most of the work the two-thirds- 



458 



APPENDIX. 



inch and one-sixth-inch objectives are most convenient. For 
determining the general structure of parts use the two-thirds 




Eye-piece. 






Fig. 175.— Parts of the Microscope. i« mol . 

a TTnMPshoebaseB Pillar. C Arm. D. Main tube or body, to the lower 



P. Mirror bar. Q. Screw-substage. By the 



of fine adjustment. M. Stage. 

^^^^^^S^S^^^^^^-aTt^iA^ of the way as 
desired. S. Iris diaphragm. 

objective, but for examining any particular part more 
minutely, use the one-sixth objective. 



THE MICROSCOPE. 459 

In vising the eyepieces, the two-inch eyepiece gives 
greater clearness, bnt less magnifying power, than the one- 
inch eyepiece. It should he kept in mind that as we increase 
the magnifying power, we lose light, and hence the need of 
special illumination for the higher powers. The mirror is 
for illuminating the object. The cone of light for illu- 
mination may be regulated by means of the diaphragm, the 
opening of which may be increased or decreased by the 
proper movement of the lever of the iris diaphragm. For 
the lower powers a large opening and the plane mirror 
should be used; for higher power, smaller opening and con- 
cave mirror. The size of the opening of the diaphragm 
should be inversely as the power; i. e., the higher the power, 
the smaller the opening of the diaphragm. In using the 
condenser, always use the plane mirror. 

Focusing. — In examining a slide, be careful to have up 
the side on which the object is mounted, and bring the part 
of the object to be examined near the center of the stage 
so as to be in line with the objective and eyepiece. If a 
two-thirds objective is used, bring the objective to within one 
half inch of the surface of the slide. To do this, turn down 
the rack and pinion adjustment (the coarse adjustment). 
Look through the microscope at the object, and gradually 
turn the coarse adjustment toward you until the object comes 
in view; bring the object to a clearer view by means of a 
few turns of the fine adjustment. In using the one-sixth ob- 
jective, the objective should be brought very near the surface 
of the object, but being careful not to touch the cover glass ; 
focus by turning the coarse adjustment toward you. 

Finding the Object. — The best method is to get the part 
of the object to be examined in the center of the field of the 
microscope by examination with the two-thirds objective; 
then reverse the objectives, and examine with the one-sixth 
or one-eighth as desired. In working with the slide to bring 
it into position, remember that the image on the microscope 
is inverted, and hence the movements are the opposite of 
what they appear to be when looking through the microscope ; 
i. e., if we desire to have the object appear to move to the 
right in the microscope, it should be moved to the left; to 
move up, it should be moved down. 

The Oil Immersion. — For objectives higher than one- 
eighth, oil immersion lenses should be used. To use the oil 



460 APPENDIX. 

immersion lens, bring the object desired for examination 
into focus by means of the one-sixth objective. If the micro- 
scope does not have a triple arm nosepiece, replace the one- 
sixth objective by the one-twelfth or the one-sixteenth oil 
immersion objective. Place over the object to be examined 
a drop of the immersion oil, and bring, by means of the 
coarse adjustment, the objective in contact with the surface 
of the object; turn the substage condenser so as to bring 
it under the object; illuminate the condenser by the plane 
mirror, and adjust the mirror and condenser so as to con- 
dense the light on the object. Gradually focus toward you 
by the coarse adjustment. For clearer definition use the 
fine adjustment. 

The Joint. — The purpose of the joint is to enable the 
tube of the microscope to be bent at a convenient angle for 
observation. To incline the stand, always grasp it by the 
pillar, and never by the tube. 

CARE OF THE MICROSCOPE. 

1. Keep it protected from the dust as much as possible, 
and when not in use, keep it covered with glass bell- jar or 
some other suitable cover. If dust collects on the instrument, 
remove it first with a camel's-hair brush, and then wipe 
carefully with chamois skin. 

2. Never wash the parts of the microscope with alcohol, 
and under no conditions use alcohol on the objectives or eye- 
pieces. 

3. Let no one except those who have been instructed in 
the use of the microscope, handle the microscope or the acces- 
sories. 

4. Avoid exposure of the microscope to direct sunlight or 
to extremes of temperature. 

5. When handling the stand, grasp it by the pillar or 
stage. While the arm is the most convenient part, it is also 
the most dangerous part to the fine adjustment. 

6. Always handle the instrument with great care, and 
avoid any sudden jars to the instrument. 

7. Kemove Canada balsam and like substance with a 
cloth moistened with benzole, and then wipe dry. 

8. If the pinion works loose, tighten by the screws on the 
pinion covers. 

9. Never use a common screw driver in setting the screws 
of the instrument, but one with parallel sides, and which 
just fits the slot of the screw. 



RULES FOR DISSECTION. 461 

10. Care of Objectives and Eyepieces. — They should be 
kept from extremes of temperature. If dust collects on 
them, it should be first removed with a camel's-hair brush, 
and then by rubbing with a chamois skin. Never use a 
chamois skin until it has been washed several times. To 
determine if the dust is on the eyepiece or the objective, 
rotate the eyepiece, and if on the latter, the spots of dirt 
will move with it, but if on the objective the spot will not 
change position by the rotation of eyepiece. Never touch the 
glass of the objective or eyepiece with the fingers. To clean 
the surfaces, breath upon them, and wipe dry with clean 
linen cloth. If lint adheres to the glass, it may be removed 
with a camel's-hair brush, or by blowing upon the surface. 
Always clean an immersion lens immediately after use. Re- 
move the fluid with moist cloth, and wipe clean with dry 
cloth or lens paper. 

II. GENERAL RULES EOR DISSECTION. 

Preparing the Specimen. — For the most part the speci- 
mens required for the work of this book may be obtained of 
a butcher, and such parts only as are needed for the work 
in view need be taken to the class or put in the hands of the 
pupils. As far as possible, remove from the specimen all 
unnecessary parts, so that the whole attention may be di- 
rected to the subject under consideration. 

Killing Animals for Dissection. — In dissection for school 
work do not use the cat or dog ; use instead a rabbit or rat, as 
these will not offend the finer feelings which pupils have for 
the domestic animals. In college work there is no objection 
to the use of the cat or dog, provided these are secured with 
the consent of the owners. In all the work avoid any signs 
of cruelty. The killing of the animal should be as painless 
as possible, and conducted so that there will be no injury to 
the tissues of the animal. If you do not have an anaesthetic 
box, a box of sufficient size to cover the animal will do. 
Place a newspaper on the floor or table, and invert over it 
the box. Put the animal under the box, and pour 10 or 15 
c.c. of chloroform on a sponge or a piece of cotton as large 
as your fist, and put it under the box with the animal, keep- 
ing the box closed. Have a good draft in the room, and avoid 
breathing the chloroform. As the animal comes under the 
influence of the chloroform, there will be more or less of a 
struggle, and it will be necessary to hold the box down, or 



462 APPENDIX. 

put a heavy weight on it. From ten to twenty minutes will 
be required to kill the animal. If you do not notice signs of 
sleeping in five or ten minutes, the dose of chloroform may 
be repeated. Do not dissect the animal until all signs of life 
have disappeared. The amount of chloroform required to 
kill an animal varies with the size and nature of the animal 
and the tightness of the box used. Turtles require a very 
large amount. After the animal is killed, parasites that may 
be on the animal may be killed by benzine. This should be 
put on the. sponge the same as the chloroform, and placed 
under the box with the animal, and kept there for ten or fif- 
teen minutes, which in most cases will kill the parasites. 

A good-sized dissecting board should be used, so as to 
avoid staining or injuring the table. The four corners of the 
board should be provided with screw-eyes or hooks, so that 
the limbs of the animal may be tied firmly in their place 
while dissecting. Plenty of sponges and absorbent cotton 
should be provided. All the waste parts should be thrown in 
the waste pail. Charcoal, potassium permanganate (a sat- 
urated solution), and sulphate of iron, or formalin, may be 
used to deodorize the pails and the animal for dissection. Of 
these, formalin (formaldehyde) is to be preferred for con- 
venience and economy. 

Dissection Wounds. — Care should be taken not to wound 
the hand with the dissecting instruments or by sharp points 
of bones, especially if the animal has been killed some time. 
If you are to handle specimens of animals that have been 
killed for some time, before beginning the dissection it is 
best to rub the hands with carbolated vaseline. This will 
prevent the absorption of any poisonous material which may 
exist in the specimen. Kever dissect if the skin of the hand 
is broken, if the specimen has been killed some time, or putre- 
faction has set in. If wounds should occur during dissec- 
tion, they should be treated at once with strong carbolic or 
nitric acid. 

After dissecting, the instruments used should be thor- 
oughly cleaned, and sterilized with a thirty-per-cent solution 
of carbolic acid. 

The waste from the dissection should be thrown iuto the 
furnace, and burned ; or if thrown out, should first be treated 
with a solution of corrosive sublimate, and thrown where 
it will not contaminate the water or the air. 



TABLE OP TESTS. 



463 



III. TABLE OF TESTS. 



TEST. 


REAGENT. 


REACTION. 


APPLICATION AND 
REMARKS. 


Acids : — 








Acetic. 


Ferric chloride. 


Dark red solu- 


Add the acid to 






tion ; on boiling 


be tested to a 






gives a brownish 


solution of fer- 






precipitate. 


ric chloride, and 
boil. The acid 
has the odor of 
vinegar. 


Arsenic. 


Copper sulphate 


Apple green pre- 


Add to a solu- 




and ammonium 


cipitate of ar- 


t i o n of copper 




hydroxide. 


senic is present. 


sulphate a few 
drops of am- 
monia hydroxide 
and to this the 
substance to be 
tested. 




Hydrogen sul- 


Light yellow 


Pass hydrogen 




phide. 


precipitate. 


sulphide gas 
into a solution 
of the supposed 
arsenic com- 
pound. To dis- 
solve arsenic add 
it to a solution 
of caustic soda. 


Alkalies. 


Phenopthalln. 


Red solution. 


Add reagent to 

substance. 


Carbolic. 


Red litmus 


Blue. 


Test substance 




paper. 


Violet color or 


with the paper. 




Sulphuric acid 


streaks to t h e 


To 2 c.c. of sul- 




and potassium 


solution. 


phuric acid add 




nitrate. 




an equal amount 
of acid to be 
tested and a 
small amount of 
the potassium ni- 
trate. {Hoff- 
mann's test.) 
Character- 
istic odor. 


Chromic. 


Alcohol and sul- 


Green color to 


Add a few drops 




phuric acid. 


solution and 


of sulphuric acid 






forming alde- 


to a strong so- 






hyde, having the 


1 u t i o n of the 






odor of the 


acid to be tested, 






squash bug or 


and then add the 






chinch bug. 


alcohol drop by 
drop, and note 
change. 




Ethereal solu- 


Intensely blue 


Add the reagent 




tion of hydrogen 


color. 


to solution of 




dioxide. 




the acid. (Stor- 
er's test.) 



464 



APPENDIX. 









APPLICATION AND 


TEST. 


REAGENT. 


REACTION. 


REMARKS. 


Citric. 


Ammonia. 


Yellow color. 


Heat the am- 
monia with the 
citric acid in a 
sealed tube to 
120° C. for six 
hours. Heat in 
air-bath. Blue 
when poured out 
and allowed to 
stand. (Sabanin 
and Laskowski'a 
test.) 


Hydrochloric. 


Silver nitrate. 


White precipi- 


Add solution of 






tate. 


the silver ni- 
trate to the acid. 


Hydrocyanic. 


Yellow ammo- 


Deep blood-red 


Add the am- 




nium sulphide 


solution. 


monium sul- 




and ferric chlo- 




phide to the so- 




ride. 




lution of the 
acid ; boil to re- 
in o v e excess of 
the ammonium 




* 




sulphide, add a 
drop or two of 
the ferric chlo- 
ride solution. 


Lactic. 


Bismuth hy- 


White, brittle, 


Neutralize a di- 




droxide and al- 


horn-like mass 


lute solution of 




cohol. 


precipitate. 


the acid with 
freshly precipi- 
tated bismuth 
hydroxide, and 
add alcohol to 
precipitate the 
salt thus 
formed. 


Nitric. 


Bits of copper. 


Red fumes and 


Add the acid to 






green solution. 


bits of copper. 


Oxalic. 


Lime water. 


A white precip- 


Add the solution 






itate. 


to the lime 
water. 


Phosphoric. 


Ammonium chlo- 


White crystal- 


Add the ammo- 




ride, ammonium 


line precipitate. 


nium chloride, 




hydroxide, and 




the ammonium 




magnesium sul- 




hydroxide, and 




phate. 




then the mag- 
nesium sulphate. 


Pyrogalllc. 


Ammonium h y - 


Lemon yellow so- 


Add the ammo- 




droxide. 


lution. 


nia to a solu- 
tion of acid to 
be tested. 




Nitrate of silver 


Black precipi- 


Add the carbon- 




and sodium car- 


tate. 


ate to the solu- 




bonate. 




tion to be tested, 
and then the sil- 
ver nitrate. 
The acid stains 
the skin brown. 



TABLE OF TESTS. 



4C5 



TEST. 


REAGENT. 


REACTION. 


APPLICATION AND 
REMARKS. 


Sulphuric. 


Barium chloride. 


White precip- 


Add a solution 






itate. 


of the barium 
chloride to the 
acid to be tested. 
If you do not 
have barium 
chloride, use lead 
acetate, which 
also gives a white 
precipitate. 


Tannic. 


Solution of fer- 
ric chloride. 


Black precipitate 
and solution. 


Add the ferric 
chloride to the 
acid to be tested. 


Tartaric. 


Solution of fer- 


Violet colored so- 


Add the reagents 




r o u s sulphate, 


lution. 


to the acid to be 




hydrogen dioxide, 




tested. 




and sodium h y - 








droxide. 






Uric. 


Nitric acid and 


Beautiful red 


Cover the sub- 




ammonia. 


color. 


stance with ni- 
tric acid and 
evaporate to dry- 
ness on water- 
bath ; add the 
ammonia. ( M u - 


Alcohol : — 






rex id test.) 


Methyl. 


Fats. 


Dissolves. 


Odor. 

Boiling 66° C. 

Specific gravity, 

.796. 


Ethyl. 


Potassium d 1 - 


Green mass and 


Powder the di- 


chromate and 


an aldehyde hav- 


chromate, and 




sulphuric acid. 


ing odor of 


add the sulphuric 






squash bug. 


acid, then the 
alcohol. 


Absolute. 


Dried ferrous 


Should remain 


Add the alcohol 




sulphate. 


colorless ; change 
to light green 
shows the pres- 
ence of water. 


to the dry salt. 


Alum. 


Ammonium, chlo- 


Gelatinous pre- 


To the solution 




ride, and a m - 


cipitate. 


of the alum 




monia hydroxide. 




add solutions of 








the reagents in 
the order named. 


Albumin. 


Ammonia and ni- 


Yellow precip- 


Boil the solution 




tric acid. 


itate. 


of the albumin, 
and add the 
nitric acid, then 
the ammonia. 


Ammonia. 


Hydrochlo- 


White fumes. 


Put the hydro- 




rlc acid. 




chloric acid in 
one test-tube and 
the liquid to be 
tested in an- 
other, bringing 
the mouths of 
the tubes to- 
gether. 




Copper sulphate 


Peep blue solu- 


Add a few drops 
of solution to be 




solution. 


tion. 








tested to the cop- 








per sulphate so- 








lution. 



30 



466 



APPENDIX. 



Antimony. 



Atropin. 



Bile : — 
Acids. 



Pigments. 



Blood. 



Caffeine. 



Calcium. 



Cholesterin. 



Carbonates. 



REAGENT. 



Water. 



Hydrogen s u 1 - 
phide. 

Sulphuric Acid. 
Potassium d i - 
chromate. 

Fresh solution of 
sugar and dilute 
sulphuric acid. 



Chloroform and 
nitric acid. 



Tinct. guiaci and 
oil of turpentine. 



Solution of red 
mercuric oxide 
in potassium 
iodide. 



Oxalic acid. 



Concentrated sul- 
phuric acid di- 
luted with one 
fifth its volume 
of water. 



Hydrochlo- 
ric acid and lime 
water. 



Curdy precip- 
itate. 

Orange precip- 
itate. 

Odor of bitter al- 
monds. 



Yellowish red 
color, passing 
into crimson. 



Play of colors, 
finally ruby-red. 



Blue color. 



Crystalline pre- 
cipitate. 



White precip- 
itate. 



Solution of sub- 
stance with red 
color. 



White precip- 
itate. 



APPLICATION AND 
EEMARKS. 



Add the anti- 
mony chloride to 
the water. 
Add reagent to 
solution to be 
tested. 

Add the reagents 
to substance to 
be tested. 

Add a few drops 
of liquid to be 
tested to the re- 
agents. (Petten- 
kofer's test.) 
Shake liquid 
with the chloro- 
form; decant ; 
allow liquid to 
evaporate ; add 
a drop or two of 
nitric acid. 
Shake the solu- 
tion of reagents 
to an emulsion, 
and add the so- 
lution to be 
tested. Examine 
drop of solution 
for corpuscles. 
Add reagent to 
liquid to be test- 
ed. Other alka- 
loids give granu- 
lar precipitates. 
Add solution of 
the reagent to 
solution of sub- 
stance to 
be tested. 

On a glass under 
the microscope 
add reagent to 
substance to be 
tested. The ad- 
dition of iodine 
gives violet col- 
o r . ( M o I e - 
schott's test.) 
Put solution of 
carbonates into a 
flask provided 
with thistle tube 
and delivery 
tube ; add acid 
through the 
thistle tube to 
the solution ; 
connect the de- 
livery tube with 
test tube con- 
taining the lime 
water. 



TABLE OF TESTS. 



467 



TEST. 


REAGENT. 


REACTION. 


APPLICATION AND 

REMARKS. 


Chloral (hy- 


Gum camphor. 


The two solids 


Rub together the 


drate) 




form a liquid. 


two solids. 




Concentrate solu- 


Blue solution. 


Warm the sub- 




tion of dichro- 




stance to be 




mate of potas- 




tested with the 




sium, nitric acid. 




dichromate solu- 
tion, and then 
add the nitric 
acid. 

Odor of chloral 
is characteristic. 


Chloroform. 


Hydrogen sul- 


.Intense blue 


Pass the hydro- 




phide. 


color. 


gen sulphide* gas 




Piece o f copper 




through the chlo- 




v.- ire. 




roform contained 








in a flask pro- 
vided with a jet 
tube ; then ignite 
gas as it comes 
from the jet 
tube ; hold wire 
in the flame. The 
odor of chloro- 
form is charac- 
teristic. 


Chondorin. 


Tannic acid. 


G i v e a precip- 


Add the acid to 






itate. 


a solution of the 

substance to be 

tested. 

Gelatin gives no 

precipitate with 

tannic acid. 


Caseinogen. 


Magnesium sul- 
phate. 


Curdy precip- 
itate. 


Add the mag- 
nesium sulphate 
to the liquid to 
b e tested until 
the solution is 
saturated. 


Elastln. 


Neutral solution 


Crimson or pink 


Heat the solu- 




of mercuric ni- 


solution or pre- 


tion of the sub- 




trate. 


cipitate. 


stance to be 
tested with the 
reagent. 


Ether. 


Small pieces of 


Boils. 


Fill test tube 




glass. 




half full of 
ether, add num- 
ber of small 
pieces of glass. 
The liquid o f 
ether should boil 
on being held in- 
closed in the 
hand. Ether Is 
more volatile 
than chloroform. 


Fat (in tissues). 


Weak solution of 


Black color. 


Stain tissue with 




osmic acid. 




reagent. 


Gelatin. 


Water. 


Absorbs water, 


Add water to 






but does not dis- 


substance. (Lea's 






solve. 


[Carey] test.) 



468 



APPENDIX. 



Glucose. 

Glycogen. 
Glycerin. 



"Hypo" (thio- 
sulphate 
of soda). 

Iodine. 
Iodates. 

Iron. 

Kreatinin. 
Lead (salts). 
Magnesium. 

Morphine. 
Opium. 



REAGENT. 



Acid solution of 
mercuric nitrate. 

Fehling's solu- 
tion. 



Solution 
of iodine in po- 
tassium iodide. 
Carbolic acid, 
sulphuric acid, 
and ammonia. 



Lead acetate. 

Silver chloride. 
Starch paste. 

Starch paste. 
Chlorine water. 



Hydrochlo- 
ric acid, ferro- 
cyanide of potas- 
sium. 

Dilute solution 
of ferric chlo- 
ride. 

Strong solution 
of dichromate of 
potassium. 

Ammonia, hydro- 
gen d i s o d i u m 
phosphate. 



Sulphuric acid 
solution of so- 
dium sulphide. 



Persulphate o f 
iron. 



Red solution. 

Brown red pre- 
cipitate. 



Deep red color. 



Carmine red 
color. 



Black 
cipitate. 



pre 



Dissolves. 

Black or purple 

color to the 

paste. 

Black or purple 

color to the 

paste. 



Blue precipitate 
or colored solu- 
tion. 



Dark-red color 
increased by 
warming. 

Orange yellow 
precipitate. 



White pre- 
cipitate. 



Flesh color, vio- 
let, dark green. 



Tied color. 



APPLICATION AND 
REMARKS. 



Add the reagent. 

Add the reagent 
to a solution of 
the substance to 
be tested ; boil. 

Add the reagent 
to the solution. 

Evaporate liquid 
to dryness, and 
heat to 120° C ; 
add two drops of 
the carbolic acid 
and the sul- 
phuric acid, dis- 
solve in water, 
and then add the 
ammonia. 

Add reagent to 
solution of sub- 
stance. 

Add the reagent. 
Add the iodine 
solution to the 
paste. 

Add solution of 
Iodates to the 
starch paste; 
add a few drops 
of the chlorine 
water. 

Dissolve the iron 
In the hydro- 
chloric acid ; add 
the ferrocyanide 
of potassium. 
Add reagent to 
substance tested. 
( T h u d i - 
chum's test. ) 
Add the sol. of 
the dichromate 
to a solution of 
the lead salts. 
Add to the solu- 
tion of the mag- 
nesium salt the 
ammonia, and 
then the phos- 
phate solution. 

Dissolve the mor- 
phine in the sul- 
phuric acid ; add 
two or three 
drops of the so- 
d i u m solution ; 
heat cautiously. 

Add the reagent 
to substance to 
be tested. 



TABLE OF TESTS. 



469 



Peptone. 
Phosphates. 

Potassium. 
Protelds. 

Pus. 



Quinine. 



Salts : — 
Bromides. 
Carbonates. 
Chlorides. 
Citrates. 
Iodides. 
Nitrates. 

Sodium. 



Starch. 
Strychnine. 



Tannin. 



Potassium h y- 
droxide and cop- 
per sulphate. 



Hydrochlo- 
ric acid, ammo- 
nium molybdate. 



Platinum chlo- 
ride (PtCl 4 ). 

Concentrated hy- 
drochloric acid. 



Alcoholic solu- 
tion of guaiac. 
Potassium iodide. 



Chlorine water. 
Powdered potas- 
s i u m ferrocy- 
anide. 



Sulphuric acid. 

Sulphuric acid. 

Sulphuric acid. 

Sulphuric acid. 

Sulphuric acid. 

Sulphuric acid. 

Potassium pyro- 
antimonate. 

Iodine solution. 



Sulphuric acid 
and potassium 
chlorate. 
Chromic acid. 



Ferric chloride 
solution. 



Purplish red so- 
lution. 



Yellow precip- 
itate. 



Yellow precip- 
itate. 

Violet red color. 



Blue color. 



Pink to deep red 
color. 



Gives precipitate. 



Blue to 
black color. 



blue- 



Maroon-red color. 



Violet color 
(Brieger's test.) 



Black ink solu- 
tion. 



APPLICATION AND 
REMARKS. 



Add to solution 
of peptone 
a strong solution 
of potassium hy- 
droxide, then the 
solution of cop- 
per sulphate. 
To a solution of 
the phosphate 
add a few drops 
of the acid, and 
then a solution 
of the ammo- 
nium salt. 
Add reagent to 
solution of po- 
tassium salt. 
Boil substance 
with reagent. 
( L i e b e r - 
mann's test.) 
Expose the solu- 
tion of the gu- 
aiac until it 
turns green on 
the addition of 
the solution o f 
potassium iodide. 
Then add reagent 
to the solution 
of pus. 

Add the sub- 
stance to the 
chlorine water, 
and then add the 
ferrocyanide. 

Add the sul- 
phuric acid, and 
test for acid thus 
formed, as hydro- 
bromic, etc. 
See tests for 
acids. 

Add reagent to 
solution of the 
sodium salt. 
Make a starch 
paste and add re- 
agent. 

Add the potas- 
sium chlorate to 
the acid. Add 
chlorate very 
carefully, as the 
action of the acid 
is quite violent. 
Add the reagent 
to solution 
tested. {Slater's 
test.) 

Add reagent to 

substance to be 
tested. 



470 



APPENDIX. 



Theobromine. 



Tin. 



Urea. 



Urine : — 
Albumin. 



Pus. 
Sugar. 

Uric acid. 

Water : — 
Hardness. 



REAGENT. 



Chlorine water. 
Ammonia. 



Hydrogen s u 1 - 
phide. 



Potassium hy- 
droxide. 

Alcohol and con- 
centrated nitric 
acid. 



Nitric acid and 
ammonia. 



See above. 
Fehling s o 1 u - 
tion. 

Nitric acid and 
ammonia. 



Purple color. 



Brown sulphide. 



precip- 



Whi te 

itate. 

Six-sided crystals 

of urea nitrate. 



Y e 1 1 o 
cipitate. 



w pre- 



APPLI CATION AND 
REMARKS. 



Add substance to 
chlorine water, 
and evaporate to 
dryness ; add the 
ammonia. 



Add the solution 
of the hydrogen 
sulphide to solu- 
tion of the sub- 
stance. 

Add reagent tc 
the substance. 
Evaporate sub- 
stance to consist- 
ency of syrup ; 
add the alcohol, 
and then distill 
off the alcohol ; 
add the nitric 
acid. 

Boil the urine ; 
add the nitric 
acid, and then 
add the ammonia. 



Red-brown pre- Add the reagent 
cipitate. to the urine, and 

boil. 
Beautiful red 
color. 



Organic impu- Solution of po- 
rities. tassium perman- 

ganate. 



Nitrates. 



Solution decolor- 
ized by organic 
substance. 



Test for calcium 
and magnesium. 
Add the water to 
the reagent, and 
set away in 
warm place for 
twenty- 
four hours. 
See test for ni- 
trates. 



POISONS AND THEIR ANTIDOTES. 471 



IV POISONS AND TIIEIE ANTIDOTES. 

SOUKCES OF THE COMMON" POISONS. 

Acetic acid — Vinegar, sugar of lead. 

Acid, carbolic — In many disinfecting washes. 

Acid, pyrogallic — In most developers used in photography. 

Acid, tartaric — In artificial lemonades. 

Antif ebrin — The free drug and in antikamnia, a common 
headache powder. 

Arnica — In many liniments. 

Arsenic — In wall paper, glazed cards, insect powders, many 
ague medicines, in some paints, many sprays for 
trees and bushes (Paris green). 

Atropin — In the leaves and berries of many of the plants 
of the Nightshade Family, in many plasters. 

Chloral hydrate — In some headache and toothache med- 
icines. 

Chloroform — In some cough medicines. 

Coal gas (Carbon monoxide) — From burning of charcoal, 
as in " self-heating " irons, etc. 

Copper and its salts — Brass spoons and vessels. 

Digitalis — Some cough medicines, many heart and kidney 
cures. 

Ergot — Rye bread. 

Fungi (Muscarine) — Mushrooms, toadstools, and truffles. 
It should be remembered that there are no sure 
rules for telling the nonpoisonous forms from the 
poisonous forms, and, unless the specimen is known 
to be nonpoisonous, it is not safe to experiment. 

Iodine and its compounds — In many medicines, especially 
in combination with sarsaparilla. 

Lead and its compounds — From the solder in cans, from 
lead pipes and paints. 

Niter (Potassium nitrate) — Sugar-cured meats. 

Opium and opiates — ■ Laudanum, paregoric, soothing syrups, 
many cough medicines, medicines for relieving pain. 
Remember children bear opiates poorly. Begin 
with the minimum dose, and watch carefully its 
effect. 

Phosphorus — In matches and some insect powders. 



472 APPENDIX. 

Ptomains — In milk, meat brines, canned meats, putrefied 

flesh, dissection wounds. 
Tin and its salts — • From acid fruits in tin cans. 
Wintergreen — Flavoring of many medicines and candies. 

GENERAL RULES TO BE OBSERVED IN CASES OF POISONING. 

1. If the symptoms are serious, get a physician at once. 

2. Inquire quickly into the history of the case. 

3. Notice odor of the breath, nature and color of the 
excreta, any stains about the person or clothing. 

4. Notice condition of the pulse, the respiration, and 
the pupils. 

5. Notice the temperature; and if low, warm the body 
by friction and hot application to the extremities. 

6. In case of weak heart, give heart stimulant, such as 
strong coffee, diluted ammonia, or aromatic spirits of am- 
monia. 

7. If the patient can swallow, drinking hot water stim- 
ulates the respiration. Vapor of ammonia or ether stim- 
ulates the respiration. 

8. For vegetable poisons use mustard as an emetic; let 
patient drink freely of warm water; keep patient awake; 
give strong coffee as a stimulant. If the patient cannot swal- 
low, the coffee may be given by rectal injection. 

9. Acids are corrosive and cardiac and respiratory de- 
pressants; hence, give something at once to neutralize the 
acid, as lime, magnesia, chalk, and mucilaginous drinks to 
counteract the corrosion of the acid; stimulants to support 
the respiration and the heart. 

10. Alkalies 1 are irritants and depressants ; give, there- 
fore, demulcent drinks, as milk, oils, and organic acid, as 
vinegar or lemon juice, to counteract alkali. Do not use 
emetics in case of alkalies. 

11. In case of threatened failure of the respiration use 
artificial respiration. 

12. Do not get excited. Keep up the courage of the 
patient. 

i Ptomains are sometimes called putrefactive alkaloids on account of their 
basic nature and the alkaline medium in which they are formed. In their gen- 
eral action they are irritants, causing nausea, vomiting, and severe pain. In 
their more specific action, they may be grouped into those acting like (1) mor- 
phine, (2) digitalis, (3) nicotine, (4) Strychnine, (5) Atropin, (6) Veratrine. 
Give gastric and intestinal antiseptics, as salol or bismuth naphtolate, in addi- 
tion to other remedies, 



TABLE OF POISONS. 



473 



TABLE OF POISONS. 
(Compiled from " Gould's Illustrated Dictionary of Medicine.) 



Acetanalid. 



Acid : — 
Acetic. 

Arsenous. 

Arsenic. 

Carbolic. 



Chromic. 



Hydrochloric. 



Hydrocyanic. 



Lactic (con 

centrated). 

Nitric. 



Oxalic. 
Pyrogallic. 

Salicylic. 

Sulphuric. 

Tartaric. 
Alcohol. 



SYMPTOMS OF POISONING. TREATMENT AND ANTIDOTES. 



A bluish discoloration of the 
skin, extreme weakness and 
depression. 

Corrosive. 

Vomiting ; purging ; sour- 
ness of the breath ; pain in 
stomach. 
See arsenic. 
See arsenic. 

Burning pain from mouth 
to stomach ; mucous mem- 
brane of mouth and throat 
white; dizziness ; uncon- 
sciousness ; low tempera- 
ture ; pupil contracted ; 
characteristic odor. 

Yellow stains on mouth and Emetics ; chalk, lime water, 



Keep body warm ; heart 
stimulants ; strychnine ; ar- 
tificial respiration if nec- 
essary. 

Alkalies ; soaps. 
Alkalies ; soaps ; mucilagi- 
nous drinks; opiates (but 
given with great caution). 



Emetics ; magnesium sul- 
phate ; opiates to relieve 
the pain ; alcohol or atro- 
pin ; a syrup of lime. 
Warm application to feet. 



mucous membrane, abdom 
inal pains and vomiting ; 
extreme depression. 
Pain throughout digestive 
tract ; vomiting ; 'feeble 
pulse ; clammy skin ; great 
depression ; blistering of the 
flesh ; yellow stains on 
clothing, but not on skin. 

Labored breathing ; vomit- 
ing ; purging ; spasm ; rigid- 
ity ; irregular heart ; char- 
acteristic odor. 



Severe irritations of the ali- 
mentary canal. 
Yellow stains on the skin : 
other symptoms like sul- 
phuric acid. 

Hot, acrid taste ; burning ; 
vomiting ; extreme depres- 
sion. 

Vomiting, diarrhea, fever, 
rigor, black urine, very la- 
bored breathing. 



milk, or albumin ; mucilag- 
inous drinks. 

Alkalies ; demulcent drink ; 
oil ; stimulants. 



Dilute ammonia ; heart stim- 
ulant (atropin) ; opiates, to 
relieve the pain ; alternate 
application of cold and hot 
water to the body ; artificial 
respiration. 
Alkali and demulcent drinks. 

Alkalies, demulcent drinks, 
and stimulants. 

Lime water, chalk, and de- 
mulcent drinks. 

Mineral acids ; alkalies ; 
salts of iron. Watch the 
respiration and the heart. 
Give stimulant if necessary. 
Stimulants ; alcoholic drink. 



Dilated pupil ; quick and 
deep respiration; more or 
less delirium ; low arterial | 
pressure; roaring in the 
ears, with deafness; rapid) 
pulse. 

Black stains (see hydro- 
chloric acid) : profuse and 
bloody salivation. 
Pain in abdomen ; vomiting ; Magnesia ; lime ; soap 
depression. 

Confusion of thought : diz- 
ziness ; staggering ; flush of 
face ; livid lips ; convul- 
sions ; depression ; coma ; 
breath the odor of alcohol. 



Chalk or limewater ; mag- 
nesia ; soap; demulcent 
drinks. 



Emetic : strong coffee ; hot' 
and cold douches of water ; 
amyl nitrite. 



474 



APPENDIX. 



Ammonium and 
its compounds. 



Aniline. 



Antifebrin (see 
Acetanilid). 
Antimony and its 
salts. 



Antipyrin. 



Arnica. 



Arsenic and its 
compounds. 



Atropia (Night 
shade, Bella- 
donna). 
Atropin. 



Caffeine. 



Calcium (see 

Lime). 

Camphor. 



Cannabis indica 
(Indian hemp). 



SYMPTOMS OF POISONING. TREATMENT AND ANTIDOTES. 



Burning pain in mouth, 
chest, and stomach ; swollen 
lips and tongue ; labored 
breathing ; vomiting of 
blood ; characteristic odor. 
Dizziness, apparent intox- 
ication, sweating, blue color 
of mucous membrane of 
mouth ; odor of aniline. 



Metallic taste, difficulty in 
swallowing, violent vomit- 
ing, pain and burning in 
the s t o m ac h , purging ; 
cramps ; great depression. 
Headache ; blue color of the 
skin ; dizziness ; drowsiness ; 
confusion of ideas ; great 
depression and prostration. 
Transient excitement ; un- 
consciousness ; dilated pu- 
pils ; extreme depression, 
paralysis. 

Violent burning pain in 
stomach, straining in vomit- 
ing, thirst, diarrhea, burn- 
ing in the urinary passages, 
with suppression of the 
urine : sense of constriction 
and dryness of the throat ; 
feeble and rapid pulse ; in 
chronic poisoning, part 
around the eyes swollen. 



Vegetable acids ; demulcent 
drinks. 



Emetic ; stimulant for both 
heart and respiration ; arti- 
ficial respiration ; adminis- 
tration of oxygen. 



Tannic acid ; milk or oils ; 
opium ; alcohol ; ether. 



Recumbent position ; strych- 
nine ; stimulants ; artificial 
respiration. 

Give cardiac stimulants. 



Freshly precipitated iron 
hydroxide with magnesia, 
emetics, demulcents. 
To make the hydroxide, to 
ferric sulphate solution (10 
parts) add ammonia (11 
parts) ; filter, and wash 
precipitate. Magnesia, 1 
part to 75 parts of water. 
Add the magnesia solution 
to a solution of hydroxide 
(iron 25 to 50 parts of 
water). Give in large and 
frequent doses. Keep the 
two solutions in separate 
bottles, ready for use when 
needed. 



Give emetics ; give strong 
coffee ; k e e p extremities 
warm ; artificial respiration. 



Emetics, morphine and 
stimulants, warmth. 



Heat and drynesis of the 
mouth and throat, suppres- 
sion of the saliva, difficulty 
in swallowing, great thirst, 
indistinct vision, great di- 
lation of the pupils, de- 
lirium, skin dry and flushed, 
very rapid pulse. 
Burning pain in the throat, 
dizziness, faintness, abdom- 
inal pain, great thirst, dry 
tongue, tremor of extrem- 
ities, weak pulse, cold skin, 
increased flow of urine. 



Characteristic odor, weak- Emetics, stimulants, 
ness, dizziness, indistinct warmth, hot and cold 
vision, delirium, convulsions, douches, 
clammy skin, smarting of 
urinary organs, feeble but 
rapid pulse. There is no 
pain, vomiting, or purging. 
Pleasurable intoxication, di- 
lated pupils, sense of pro- 
longation of time, tremor 
of the limbs, weakness. 



Strychnine, stim- 
ulants, evacuation. 



TABLE OF POISONS. 



475 



C a n t h a r i 
(Spanish fly). 



Carbolic acid 
(see Acid). 
Carbon D I s u 1- 
p h i d e (Bisul- 
phide). 

Chloral hydrate. 



Chlorine. 



Chloroform. 



Citric acid (see 

Acid). 

Coal gas. 



Cocain. 



Copper and its 
salts. 



Creosote (see 
Carbolic Acid). 
Cronton tiglium 
(Croton oil). 



Cyanogen and its 
compounds. 
Datura stramo- 
nium (James- 
town Weed). 



SYMPTOMS OF POISONING. TREATMENT AND ANTIDOTES. 



Tenderness o f t h e ab- Emetics, demulcent drinks, 

domen, mucous or bloody morphine. 

stools, vomit mucus and 

containing shiny particles,! 

blood and albumin i n 

urine. convulsions, coma, 

unconsciousness. 



Headache, dizziness, excite 
ment, rigor of the muscles 
characteristic odor in 
breath and discharges. 
Deep sleep, loss of muscular 
power, slow respiration and 
weak pulse, pupils contract- 
ed during sleep, but dilated 
when awake. 



Characteristic odor, irrita- 
tion of the throat and air 
passages, sense of tight- 
ness across the chest ; swal- 
lowing difficult. 
At first slight stimulation, 
excitement (in reality, de- 
pression), incoherent speech, 
relaxation of muscles, and 
insensibility. 



Odor of gas, headache, diz- 
ziness, suffocation, loss of 
muscular power, uncon- 
sciousness, dilated pupils, 
labored respiration. 
Feeling of faintness, dizzi- 
ness, weak, nausea, rapid 
and intermittent pulse, ex- 
treme prostration, slow and 
feeble respiration. 
Metallic taste in the mouth, 
thirst, black decoloration 
of mucous membrane, grip- 
ing and colicky pain, nau- 
sea and vomiting, purging 
with straining, hurried res- 
piration, weak but rapid 
pulse, weakness. 



Intense abdominal pains : 
vomiting, purging, pinched 
face ; weak, thready pulse ; 
moist skin ; great prostra- 
tion. 

Same as those of hydrocy- 
anic acid, which see. 
Like those of atropin, which 
see. 



Emetics, warmth, stimula 
tion, artificial respiration. 



Emetics ; keep up tempera- 
ture by hot bottles, hot 
blankets to feet, and fric- 
tion ; keep patient awake ; 
hot coffee, heart stimulant, 
strychnine ; artificial res- 
piration if necessary. 
Fresh air ; inhalation of 
dilute ammonia, ether, or 
chloroform. 



Draw the tongae forward u 
fresh air ; heart and re- 
spiratory stimulants : rectal 
injection of normal saline 
solutions and hot coffee ; 
artificial respira- 
tion ; breathing of amyl ni- 
trite or ammonia. 



Fresh air, ammonia, arti- 
ficial respiration, s t 1 m - 
ulants, hot coffee, hot and 
cold douches. 

Heart and respiratory stim- 
ulants, amyl nitrite. 



Emetics, morphine ; poul- 
tices to stomach ; barley 
water ; demulcent drinks. 



Emetics, demulcent drinks, 
camphor. stimulant. mor- 
phine, poultices to abdomen. 



476 



APPENDIX. 



Digitalis pupura 
(Fox-glove). 



(see 



Dog bite 

Saliva). 

Ergot. 



Ether. 



Fungi ( m u s h - 
rooms, toad- 
stools, truffles, 
many species 
of which are 
poisonous). 
Insects, Poison- 
ous (the bite or 
sting). 



Iodine and Its 
compounds. 



Iodoform. 



Ipecacuanha 

(Ipecac). 

Iron and its salts. 



Lactic acid (see 
Acid). 

Laudanum (see 
Opium). 

Lead and Its com- 
pounds. 



Lime. 



Lobelia (Indian 
Tobacco). 



SYMPTOMS OF POISONING. 



TREATMENT AND ANTIDOTES. 



Purging, with severe pains ; 
vomiting, the matter being 
of grass-green color ; weak, 
irregular, and slow pulse ; 
headache, delirium and con- 
vulsions ; pupils dilated ; 
skin cold. 



Tingling of the fingers and 
feet, cramps in the extrem- 
ities, dizziness, weakness, 
dilated pupils, weak pulse, 
vomiting and retching. 
Sense of choking, cough, ex- 
citement, relaxed muscles, 
insensibility. 

Catarrh of the stomach and 
intestines, nausea, vomiting 
and purging, heat and pain, 
fainting, convulsions, weak 
and frequent pulse, pupils 
dilated, delirium, stupor. 
In most cases the symptoms 
are slight, but in case of 
tarantula, scorpion, and 
centipede, may be very seri- 
ous ; pain, swelling, fever, 
suppuration, possible gan- 
grene, and death. 
Pain In throat and stom- 
ach ; vomiting, the material 
being yellow, or, if starch 
is present, blue or nearly 
black ; dizziness, falntness. 
convulsions, singing in the 
ears, rapid pulse, ravenous 
appetite. 

Slight delirium, drowsiness 
emaciation ; fever : rapid 
pulse : symptoms like those 
of meningitis. 
Vomiting ; vomit containing 
food ; depression. 
Metallic taste, pain, vom 
iting, purging, vomited mat 
ter black. 



Emetics, tannic acid, stim- 
ulants, aconite, recumbent 
position. 



Emetics ; quick purgatives, 
Epsom salts, tannic acid, 
stimulants, recumbent posi- 
tion. 

Treat as in chloroform poi- 
soning, which see. 

Emetics, quick purgatives, 
Epsom salts, stimulants, 
atropin. 



In mild cases, ammonia or 

baking soda applied to 

wound ; soap, repeated 

washing. 

In very severe cases, treat 

same as for bite of snake, 

which see. 

Emetics, starch ; morphine ; 

chew pellitory to eliminate 

the iodine. 



Wash the wound with oil of 
eucalyptus. 



Evacuate. 

Magnesia, drink freely of 
water ; Ice, opium. 



Dryness of t h e throat 
great thirst : metallic taste 
colic relieved bv pressure , 
rigidity of abdominal mus- 
cles ; eonstioation, cramps 
In lower limbs, convulsions : 
In chronic forms blue line 
on margin of gums. 
Burning pain in abdomen; 
great thirst ; obstinate con- 
stipation. 

Severe vomiting ; great de- 
pression ; dizziness ; t r e - 
mors ; convulsions. 



Emetics, dilute sulphuric 
acid, Epsom salts, milk, 
morphine, iodide of potas- 
sium to eliminate the lead, 
poultices to the abdomen. 



Vegetable acids, demulcent 
drinks. 

Evacuate, tannic acid, stim- 
ulant, strychnine, warmth, 
recumbent position. 



TABLE OF POISONS. 



477 



NAME. 



Meat (from pro 
mains from pu 
trefaction). 

Mercury and its 

compounds. 



SYMPTOMS OF POISONING. TREATMENT AND ANTIDOTES. 



Milk (tyrotoxi- 
con). 

Morphine (see 
Opium). 

Mushrooms (see 
Fungi). 

Niters (see Po- 
tassium nitrate). 
Nitric acid (see 
Acid). 

Nux vomica (see 
Strychnine). 
Opium. 

Morphine. 

Laudanum. 



Oxalic acid (see 

Acid). 

Paris Green (see 

Arsenic). 

Peach-kernel (see 

Hydrocyanic 

acid). 

Petroleum. 



Thosphorus. 



Poison vine (see 

Rhus). 

Poison oak (see 

Rhus ) . 

Pokeberries (Phy- 
tolacca). 

Potassium and its 
compounds. 



Prusslc acid (see 

Hydrocyanic 

acid). 



Severe irritation of stomach 
and intestines, nervousness, 
prostration. 

Acrid metallic taste : burn- 
ing sensation in throat and 
stomach : vomiting ; diar- 
rhea, with bloody stools : 
lips and tongue white and 
shriveled ; pulse weak and 
frequent : coma. Secondary 
symptoms : Hectic fever, 
coppery taste, fetid breath, 
gums swollen, salivation. 
Nausea, diarrhea, cramps, 
prostration. 



At first, excitement, quick- 
ened pulse ; later, headache, 
weariness, sensation of 
weight in limbs, stupor, 
diminished sensibility, con- 
tracted pupils ; person diffi- 
cult to arouse ; reflexes 
abolished : jaw falls, res- 
piration slow, irregular, and 
stertorous ; pulse weak. 



Burning in alimentary tract, 
excreta covered with layer 
of oil, skin cold, feeble but 
regular pulse, respiration, 
sighing, thirst, restlessness. 
Vomiting and pain : garlicky 
odor to breath : vomit may 
be luminous in the dark, 
and has odor of phosphorus : 
heart weak ; tendency to 
hemorrhage : coma or de- 
lirium ; albumin in urine. 



Nausea, vomiting, depres- 
sion, pulse and respiration 
weak, tetanic convulsions. 
The hydrates and carbon- 
ates act like lime, which 
see ; the salts like acid, 
from which they are de- 
rived. 



Emetics, purgatives, seda- 
tives, stimulants in case of 
prostration or weakness. 
Albumin in some form, raw 
white of egg or flour, evac- 
uate, potassium iodide, 
opium. 



Emetics, intestinal antisep- 
tics, stimulants. 



Evacuation ; keep person 
awake ; ammonia, strong 
coffee, atropin, strychnine, 
artificial respiration, potas- 
sium permanganate. 



Emetics, stimulants, 
warmth, stimulation of skin, 
artificial respiration. 



Sulphate of zinc or copper, 
Epsom salts. Never give 
oils or fats. 



Evacuate, alcohol, opium, 
ether, digitalis. 

Vegetable acids, demulcent 
drinks, oils. 



478 



APPENDIX. 



SYMPTOMS OF POISONING. 



TREATMENT AND ANTIDOTES. 



Pyrogallic acid 

(see Acid). 

Rhus (Poison 
vine, Poison 
Oak). 



Salicylic acid (see 

Acid). 

Saliva of Rabid 

Animals. 



Silver and its 
salts. 



Snake bite. 



Soda (Sodium) 
and its salts. 

Strychnine. 



Sulphuric acid 
(see Acid). 
Sumach (see 
Rhus). 
Tansy. 



Tartar Emetic 
(see Antimony). 
Tin. 



Tobacco (Nico- 
tine). 



Irritation of the skin ; itch- 
ing, swelling, and vesicular 
eruption; inflamma- 
tion may spread to the 
throat, producing cough ; 
thirst, vomiting, colicky 
pains, fever, delirium. 



It is rare that the symp- 
toms are shown before three 
weeks ; may occur between 
that and many years ; pain 
in bitten part ; uneasiness, 
languor, difficult respira- 
tion, difficulty of swal- 
lowing, horror of water, vio- 
1 e n t convulsions, tongue 
swollen, flow of visjcid 
saliva. 

Pain, vomiting, purging, 
vomit white and cheesy, 
turning black in the sun^ 
light ; cardiac depression. 
Vary in different cases, but 
in most cases pain in bitten 
parts and rapidly spread- 
ing ; great swelling of 
wounded part, which be- 
comes livid, and later gan- 
grenous ; fainting, vomiting, 
and convulsions ; pulse fee- 
ble, rapid, irregular ; labored 
respiration. 

Symptoms and treatment 
like that of potassium, which 
see. 

Tetanic convulsions coming 
on in paroxysms at varying 
intervals of from five min- 
utes to half an hour. 
Muscles in tetanic contrac- 
tion during paroxysm : eye- 
balls prominent, pupils di- 
lated, difficult respiration, 
pulse feeble and rapid, 
anxiety. 



Odor of tansy in breath, 
convulsions, in ■ 
sensibility, dilated pupils, 
rapid respiration, pulse full, 
gradually falling. 



Rub with Grindelia; carron 
oil and solution of acetate 
of lead ; rest, laxatives, 
opium. 



Preventative: 
immediate ligature above 
wound ; excision, cautery. 
Of hydrophobia : chloro- 
form internally, morphine, 
hypodermatically, cocain to 
throat, nutritive injections. 



Salt and water ; evacuate ; 
albumin ; stimulants. 



Removal of poison by suck- 
ing or cupping ; ligature 
above wound ; cut out 
wounded part, or cauterize ; 
ammonia to wound and in- 
ternally ; warmth ; alcoholic 
stimulants in some cases. 



Evacuate ; animal charcoal 
or tannic acid, followed by 
emetics ; keep patient quiet ; 
bromides and chloral, chlo- 
roform, artificial respiration 
in some cases. 



Heart stimulants, evacuate. 



Metallic taste, vomiting and 

diarrhea, severe pain, de 

pressed heart. 

Nausea, vomiting, great 

weakness, feeble pulse, cold 

and clammy skin, pupils lants, warmth, 

contracted and then dilated, position 



magnesia, mu- 
drinks, heart 



Evacuate ; 
cilaginous 
stimulant. 

Emetics, tannic acid, 

strychnine, stimu- 

recumbent 



TABLE OF POISONS. 



479 



Turpentine. 



Veratrum (Helle- 
bore). 



Wild Cherry (see 

Hydrocyanic 

acid). 

Wintergreen 

(Gaultheria). 

Woorara ( C u - 

rare). 



Zinc. 



SYMPTOMS OF POISONING. TREATMENT AND ANTIDOTES. 



Odor of turpentine ; intox- 
ication ; contracted pupils ; 
stertorous breathing ; coma : 
tetanic convulsions ; urine 
has the odor of violets. 
Burning pain in alimentary 
tract ; cannot swallow; 
vomiting and diarrhea ; 
palpitation at first, then 
slow, weak pulse ; labored 
respiration ; pupils generally 
dilated, convulsions in some 
cases. 



Like those of Salicylic acid, 
which see. 

Complete paralysis of the 
Voluntary muscles ; slowing 
of the heart beat and res- 
piration. 

Corrosion of the lips or 
month : pain and burning : 
Incessant vomiting, the 
vomit blood-stained : accel- 
eration of pulse and respi- 
ration : labored breathing : 
dilation of pupils ; convul- 
sions, like those of epilepsy ; 
paralysis, coma. 



Evacuate, magnesium sul- 
phate ; demulcent drinks ; 
morphine. 



Evacuate ; ether hypoder- 
matically ; opium ; stimu- 
lants ; coffee ; warmth ; re- 
cumbent position. 



Artificial respiration ; stim- 
ulants ; ligature, and wash 
the wound ; evacuate the 
bladder frequently. 



Sodium or potassium car- 
bonate, milk, eggs, tannic 
acid, morphine hypodermat- 
ically ; poultices to ab- 
domen. 



480 APPENDIX. 

V. CONTAGIOUS DISEASES. 

Micro-Organism. — " Erom dust thou art, and to dust 
thou shalt return/' is as true in the light of science as in 
the light of inspiration. It is as true of all organic beings 
as of man ; this is alike the story of the life history of the 
simple lichen and the giant Sequoia, the king of the for- 
est. The cycle for the plant is mineral, plant, mineral; for 
the animal it is but a little more continued story of mineral, 
plant, animal, mineral. 

Eorms are brought into existence, grow, attain a certain 
degree of size and power, decline, die, decay, and return to 
the elements from which they came. Mountains are brought 
into existence, attain their greatest degree of magnitude and 
grandeur, decline, crumble by the erosive forces of nature, 
and are carried into the sea, and are not. Rivers, plains, 
valleys, lakes, land, and ocean have a similar history, and, 
may we not say, the earth and all material forms ? 
Change, unceasing change, is nature's law ; organization, dis- 
organization. Yet in this ceaseless round the sum total of 
matter remains the same. Hydrogen is always hydrogen, 
carbon is carbon, and sodium is sodium, indestructible; but 
like the ever-changing forms of the kaleidoscope, they are 
ever making new combinations. To-day, gases in the air, 
salts of the earth, and constituents of water; to-morrow, 
protoplasm and cellulose of plant tissue, and then trans- 
formed into brain and muscle, bone and nerve, of some ani- 
mal form; now changed by the organism to carbon dioxide, 
water, salt, and urea, and next returned to the sources from 
which they came. Like the fabled Phoenix, the ashes of one 
form become the germinal grains of other forms. In one 
sense, we die that others may live. If it were not for this 
endless chain of changes, the elements of matter would be- 
come used up in existing forms, and there would be no 
material for the formation of new forms, or for the repair 
of the old. 

Many of these changes take place very slowly, others very 
rapidly. It has taken ages to produce a gorge of a Niagara, 
but annually millions of plants and animals die, and return 
to dust. It will take seons to level the mountains to the sea, 
but in a few hundred years all living forms (except the im- 
mortal part of our being — the soul) of earth, air, and 



FERMENTS. 481 

sea will have disappeared, and will have returned to the ele- 
ments from which they came. The forces by which these 
changes are produced are also indestructible, and, like matter, 
are ever changing their forms from molar to molecular, mo- 
lecular to ethereal, physical to chemical ; now potential in its 
chemico-vital to physical or chemical, chemico- vital, and 
form, then kinetic ; kinetic, then potential. In all this varied 
transformation, the sum total of energy remains the same. 

Some of these forces are constructive; i. e., they so com- 
bine the elements of matter as to make it more complex, 
both as to its structure and properties ; others act upon these 
complex substances, and reduce them to simpler forms. We 
have seen both of these forces at work in our study of the 
human body, and similar changes are taking place in every 
organism, in the plant and animal alike, and even organic 
products and mineral compounds are not exempt from the 
action of these forces. When the organism dies, the destruc- 
tive agents soon decompose it; the giant pine, which was 
centuries in forming its massive trunk and lofty branches, 
when uprooted by the storm, decays in a few months or 
years. The most active agencies in effecting this decomposi- 
tion, and the return of the organic substances to their min- 
eral constituents, nitrogen, hydrogen, oxygen, carbon diox- 
ide, mineral salts, and ammonia, are micro-organisms. 

Fermentation and Ferments. — The process by which these 
micro-organisms effect this decomposition is called fermenta- 
tion, and the agencies by which it is effected are called fer- 
ments. The term is here used in its broad sense, and to 
mean all those chemical changes in which a substance, min- 
eral or organic, undergoes change through the agency of an 
organic substance, derived either from the activity of plants 
or animals; the substance remaining the same in amount 
(quantitatively) before and after the reaction. 

All ferments have the following properties in common: 
(1) They are organic nitrogenous substances of either vege- 
table or animal origin; (2) they are unstable compounds, 
whose active principle is destroyed by a temperature above 
100° C, and by certain powerful reagents (such as antisep- 
tics) ; (3) a small amount of the ferment is capable of pro- 
ducing fermentation in a relatively large amount of the 
substance to be fermented. 

As to their origin, ferments are of two classes: (1) Those 
31 



482 



APPENDIX. 




1. Consumption. Bacilli. 

a, " Zeiss T V Oil-immer- 
sion, Ocular 4, tube drawn 
out. (Koch.) b. Bacillus 
tuberculosis in sputum, x 
1,000. (Baumgarten.) 



2. Pneumonia. Bacillus 
of Friedlander. 

a, From a culture, b, from 
blood of mouse showing cap- 
sule. (Flugge.) 



3. Pneumonia. Micrococcus. 

From blood of rabbit inoc- 
ulated with human saliva 
x 1,000. (Sternberg.) 




4. Diphtheria. Bacillus. 
From a culture of blood 
serum, x 1,000. (Frankel 
andPfeiffer.) 



5. Influenza. Bacillus. 

From bronchial mucus. 
x 1,000. (Frankel.) 



6. Typhoid Fever. Bacillus. 
From single gelatin colony. 
x 1,000. (Sternberg.) 




8. Anthrax. Bacillus. 



From pus. x 800. (Flugge.) 



9. Cholera. Asiatic. 
Spirillum, x 1,000. (Koch.) 



?. Erysipelas. Strepto- 
cocci. 

From a culture showing 
formation of spores, x 1,000 
(Klein.) 
FIG. 176.— ILLUSTRATIONS OF VARIOUS DISEASE GERMS. 
(Michigan State Board of Health.) 



FERMENTS. 483 

which have a definite structure, and are capable of mul- 
tiplication and growth, and hence called organic ferments 
(zy mazes) ; e. g., the yeast plant {saccliaromyces cerevisivce) ; 
(2) those, while produced by plants or animals, are unorgan- 
ized, incapable of reproduction, but may pass into a solution, 
and be recovered from the solution when desired in the same 
way as ordinary chemical compounds, and hence are called 
unformed or soluble ferments {enzymes) ; e. g., pepsin of 
the gastric juice.. 

The more important classes of organic ferments are: (1) 
Those like our common molds, fungi; (2) those like the yeast 
plant, saccliaromyces; and (3) those very small in size, of 
a great variety of forms, and reproducing by fission, bac- 
teria. The first group is not very important in the produc- 
tion of fermentation ; the second is much more important, 
being the agents which produce vinous fermentation; the 
third group is far more numerous in the number of species 
in the group, produces a much greater variety of fermenta- 
tion, and hence is more important. The first group is 
little affected by acid media, but the second is more sen- 
sitive in this respect than the first, while the third group, 
with a few exceptions, as the acetic acid ferments, is very 
sensitive to an acid media, and hence the value of acids as 
antiseptics. 

The bacteria, as to the product they make, are classed into 
three groups: those producing pigments (chromogenic) ; those 
that produce fermentation {zymogenic) ; and those that pro- 
duce disease (Fig. 176), both in plants and animals {patho- 
genic). As has been stated, they have a great variety of 
forms, but for convenience of study they may be classed into 
three groups : those made up of more or less spherical-shaped 
bodies, either isolated or grouped, micrococci ; those that are 
rod shaped, bacilli; those looking like spiral short threads, 
spirilli. Of the ferments, the bacteria are the more widely 
distributed, being found in the air, the water, the earth, 
or plants, in the various organs of animals, in cold as well 
as hot climes, though in the latter condition they are much 
more numerous. The bacteria are far more numerous as 
to the number of species and in the number in each species. 

The mode of action of ferments is too complex to be 
given in an elementary treatise, yet it is of importance for 
us to know the more general nature of these actions. They 



484 APPENDIX. 

may be stated briefly as, (1) those which produce fermen- 
tation by hydration, as the change of starch to sugar; (2) 
those producing fermentation by decomposition, as the 
changing of dextrose to lactic acid; (3) by reduction, as in 
butyric fermentation; (4) by oxidation, as the conversion 
of sugar into alcohol (ethyl alcohol). To the latter class 
belongs the class of fermentation commonly called decay. 
When the decomposition is that of a nitrogenous substance, 
and results in the production of offensive gases, the process 
is called putrefaction. The decomposition and disintegra- 
tion of albuminous material often results in the production 
of active, inanimate, septic, or toxic substances, called pto- 
mains. Many of these ptomains are poisonous ; the most of 
them, however, are not. They are found in ice cream, putre- 
fied flesh, putrefied fish, fish-brine, and other sources of putre- 
faction. Great care should be used in handling putrid ma- 
terials, hides of animals, and dead bodies, as there is great 
danger from poisoning through the broken skin, by sores, 
or wounds. Canned meats and fish should never be left in 
the cans after opening. Milk cans, crocks, and ice cream 
freezers should be thoroughly washed with boiling water 
before using. 

The action of these micro-organisms is not restricted to 
dead material or mineral substances, but many of them attack 
living organisms, and they are the cause of various diseases, 
as smallpox, consumption, and like diseases, called infec- 
tious diseases. It is a well-established fact that most of our 
diseases are due to some form of specific germ or micro- 
organism, and in our studies of these we have gained some of 
our greatest victories ; many diseases which a few years ago 
baffled the best medical skill, and destroyed annually thou- 
sands of lives, are now treated with but a very small per cent 
of loss of life, and less suffering to the patient. 

Many of these germs produce, by their action in the sys- 
tem, substances which check the further action of the infec- 
tious germ, and in many cases, if the system is strong enough 
to withstand the effects of the disease, this substance will 
entirely destroy the disease germ, and the person will recover. 
This substance is called antitoxin. If this antitoxin is taken 
from a diseased animal and given to a person just taking the 
disease, the severity and duration of the disease may be very 
much lessened, or entirely overcome. 



DISINFECTING. 485 

Some of these diseases so affect the system of the person 
having them that they render him incapable of having them 
again, or the person may be inoculated with a mild form of 
the disease, and the system become protected against the 
more malignant form; this condition of the system is called 
immunity. 

While most of these diseases are treated with great skill, 
and death has been reduced to a minimum, yet our greatest 
protection comes from their prevention. The more important 
ways by which this has been effected are : ( 1 ) The isolation 
of the person diseased so that he will not come in contact 
with others, and infect them, and thus spread the disease; 
(2) by disinfecting ; i. e., treating the clothing or articles 
used by the person, and the premises, with substances which 
kill the disease germs, and prevent contagion; (3) by remov- 
ing the conditions favorable to the growth of the germs, as 
draining the stagnant pond, cleaning the filth from the 
street, and contamination of our drinking water with sew- 
age; and (4) by keeping our houses as free from dust as 
possible, and letting in an abundance of sunlight and air. 

Disinfecting. — This is one of the most important means 
of preventing the spread of disease. For articles that can 
be boiled, boiling for twenty or thirty minutes in water is a 
very effective method of disinfecting, as there are few germs, 
if any, that are not killed by heating in water at 100° C., but 
clothes containing the expectorations of persons having 
diphtheria, scarlet fever, and consumption should be burned. 

The more important substances used in disinfecting are 
sulphur, carbolic acid, corrosive sublimate, chlorinated lime, 
and formalin. 

All vessels that can be cleaned by boiling hot water should 
be washed with corrosive sublimate (1 part of corrosive sub- 
limate to 1,000 parts water), carbolic acid, or strong chlorine 
water (ten per cent of chlorine). The fecal discharges of 
persons having typhoid fever and like diseases should be 
disinfected by mixing them thoroughly with one ounce of 
chlorinated lime and a teaspoonful of carbolic acid before 
throwing them out. 

The clothing and bedclothing of persons having smallpox 
or scarlet fever may be disinfected by putting them in a 
closed closet and fumigating them with chlorine set free from 
chlorinated lime treated with carbolic acid (two ounces of 



486 





APPENDIX. 


- _ f . _ , .. - 










: '.-V 


• • ?Af j 




•. ^\'i 3 




• 




; w\* 





■ 





Fig. 177.— The Novy Apparatus for Formaldehyde Disinfection. 
(Parke, Davis & Co., Detroit.) * 



CAUSES OF DISEASE. 487 

lime to a tables poonful of carbolic acid), leaving tliem for 
several hours. Strong acids should not be used, as they will 
set the chlorine free in such large amounts as to bleach and 
injure the clothes. The sick-room may be disinfected in a 
similar way, but by using larger amounts of the materials. 
There is no need of destroying the clothing, the beds, or fur- 
niture, as proper disinfecting will prevent any possible con- 
tagion. Formalin is a very effective disinfecting agent. A 
room may be fumigated (Fig. 177) by passing the vapor 
from a formalin still into the room by means of a tube run- 
ning from the still through, the kevhole of the door. Eight 
ounces of a forty-per-cent solution, under favorable circum- 
stances, will disinfect one thousand cubic feet of space, and 
for larger space proportionate amounts. If the vapor can 
escape through the cracks of the doors or window, due allow- 
ance must be made, and the amount proportionately in- 
creased. The vapor of formalin does not injure the most 
delicate fabrics: it rusts iron, but does not injure other 
metals. 

DISEASE I ITS MORE COMMON CAUSES AND PREVENTION". 

Causes of Disease. — Disease is a disorder of the struc- 
ture or function of the body. Its causes are numerous. The 
more important are: (1) mechanical, as an injury from a 
wound, a sprain, or a fall; (2) the result of exposure to cold 
or wet, in which the body becomes chilled, producing conges- 
tion of the internal organs, or what we call " a cold; " a 
cold should be watched with the greatest care, and means 
should be taken at once to cure it, as it lowers the tone of 
the system and makes possible the attacks of disease germs, 
which under a healthy condition may be thrown off, but in 
case of a deep cold find foothold, and develop into pneu- 
monia, consumption, or fevers; (3) improper eating, either 
as to quantity, quality, or the time and manner of taking 
the food; (-1) irregular habits, insufficient sleep, overwork, 
or a lack of exercise; (5) dissipation of any kind; (6) the 
contact with specific disease germs of contagious disease, as 
the bacilli of consumption, diphtheria, or typhoid fever. 

Many of these germs are in the air, the water, the soil, 
or in our food, and any lowering of the tone of the body 
renders it unable to throw them off. Other forms are not 
common, and are spread only by the person coming in con- 



488 APPENDIX. 

tact with the diseased persons, as in smallpox, scarlet fever, 
and measles. These germs attack the most robust. 

Prevention of Disease. — The more important precautions 
toward the prevention of disease are: (1) regularity of 
habits of eating, sleep, work, and recreation; (2) keep the 
feet and body dry, and the skin and excretory organs active ; 
(3) breathe pure air, by avoiding infected air and poorly 
ventilated rooms, and take plenty of simple, wholesome 
food; (4) avoid all narcotics and stimulants; (5) by scrupu- 
lous cleanliness, prevent the collection of dust or filth that 
may become the hotbed of disease germs ; (6) the isolation of 
persons affected with contagious diseases., and thorough dis- 
infection of rooms and articles used by persons thus affected ; 

(7) by immunity, as in case of smallpox, by vaccination, or 
by the administration of antitoxin in case of diphtheria; 

(8) by calling the attention of the health officers to any sus- 
picious sore throat or eruptive disease, and at once isolating 
the person; (9) in case of wounds and sores, to keep them 
protected from the air, and to antisepticize the bandages 
and wounds. 

DANGEROUS COMMUNICABLE DISEASES. 

The following facts have been taken from the bulletins' 
of the Michigan State Board of Health : — 

Consumption. — Consumption is a dangerous and com- 
municable disease. As shown in Fig. 178, it is the most 
fatal of communicable diseases, many times more so tham 
the so much dreaded smallpox, and in fact more than any 
other disease. Though the lungs are generally the seat of 
the disease, other parts of the body may be attacked, as the 
alimentary tract, the joints, and the lymphatic glands. It 
is spread by the dust of the dried sputum, in milk, and in 
the meat of tuberculous animals. While there is the he- 
reditary transmission, it is now established that it is a com- 
municable disease, and any one may become infected by it. 
A consumptive is a menace to public health, and if the 
proper precautions are not used, he may spread this dread- 
ful disease. The sputa should never be swallowed, as it 
will carry the contagion to the alimentary canal, and bring 
serious complications, and even general tuberculosis. 

Any person who has a habitual cough, and who coughs 
up sputa, should have the sputa examined for bacillus tuber- 



COMMUNICABLE DISEASES. 489 

culosis. Such a course is better for the person, since he may 
know his true condition ; and if bacilli are present, the dis- 
ease may be treated in its first stages, as there is hope of 
recovery if taken at this stage. It is also much better for 
the public health, as proper precautions can be taken for 
the prevention of the spread of the disease to the members 
of the family or other persons that come in contact with the 
infected person. Delay is dangerous. Every day lessens 
the possibility of recovery, and the person becomes a greater 
menace to the public health. 

Consumptives should never expectorate where the spu- 
tum may become dried, and get in the dust of the air, and 

OEATHS IN MICHIGAN, 10 YEARS, 1887-96. 

wmammBmammBmammammaammammmmmam consumption 



I PNEUMONIA. 
OIPHTHERIA. 



TYPHOID FEVER. 
SCARLET FEVER 
MEASLES 
WHOOPING-COUGH. 
I SMALL-POX. 

Fig. 178,— Relative Number of Deaths from Various Diseases. 

thus become the source of contagion. They should expec- 
torate on small pieces of cloth, and these should be burned 
at the first opportunity, and never on a handkerchief, in 
which the sputum may become dry, and be the means of in- 
fection to those handling it. 

All dejecta of a consumptive person should be destroyed 
or disinfected. A good disinfectant is chlorinated lime with 
carbolic acid, one ounce of the lime and one teaspoonful of 
acid to each discharge, or in its stead one quart of " Standard 
Solution Xo. 1." Cuspidors used by consumptives should be 
disinfected with wood vinegar. Consumptives should not 
use the same towel or drink from the same vessel used by 
others. 

Pneumonia. — This ranks next to consumption in the fatal- 
ity it produces. This is a disease of the lungs, and it is pro- 
duced by micro-organisms which gain access to the lungs, 
and which multiply rapidly. The disease has a rapid course, 
and may end fatally in five or ten days. Any one of three 
organisms may produce this disease. It is spread, like con- 
sumption, by the germs contained in the sputa. This is a 
very dangerous disease, and most prevalent in the colder 
months. All sputa should be disinfected, and great care 



490 APPENDIX. 

taken to prevent colds. Pneumonia sometimes becomes 
epidemic. 

Meningitis. — Like pneumonia, this seems to be due to 
more than one germ. It is a disease of the coverings of the 
brain and spinal cord. It frequently accompanies outbreaks 
of pneumonia, and the same germs may be present in either 
of these diseases ; in one case acting on the lung tissue, pro- 
ducing pneumonia, and in the other on the membranes of the 
brain or spinal cord, producing meningitis. The best protec- 
tion is to avoid exposure. 

Influenza, — This disease is commonly known as the 
" grippe." It has been quite prevalent for the past ten years. 
It is caused by a specific germ. These germs are found in 
the bronchial and nasal secretions and in the saliva of the 
person affected with the disease. It is sometimes fatal. It 
is often epidemic. Very frequently it is followed by pneu- 
monia or meningitis. When epidemic, it seems that the 
meteorological conditions are the primary causes for the 
lack of power to resist the germs of influenza, as well as those 
of pneumonia, meningitis, and consumption. During such 
epidemics great care should be taken of the health. The 
towels, cups, etc., used by the sick person should not be used 
by others until thoroughly washed in boiling water. 

Diphtheria. — This disease is due to a specific germ pe- 
culiar to this disease. In its activity it produces a powerful 
poison, and it is to this poison, rather than to the injury to 
the tissues of the throat, that the sickness and death from 
diphtheria is due. The bacilli may remain in the mouth 
for weeks after apparent recovery from the disease, and dur- 
ing this period they may retain their virulence, and sputa 
containing them is dangerous ; hence the importance of keep- 
ing the persons who are recovering from an attack of diph- 
theria under the same restrictions in regard to associating 
with others, and in disinfecting all vessels or articles used 
by them, for several weeks after apparent recovery. The 
fact that the " false membrane " has disappeared is no evi- 
dence that danger from contagion is over. 

In this, as in other infectious diseases, the use in common 
by pupils of pencils, chewing gum, drinking cups, or any 
other articles likely to be placed in the mouth, should be 
discouraged, and the danger of such practices explained. 



COMMUNICABLE DISEASES. 491 

Typhoid Fever. — This disease is not often contracted di- 
rectly from one sick with the disease, but usually from the 
use of food or water contaminated with the germs from care- 
lessness in not disinfecting the articles and vessels used by 
the sick person. The chief source of danger, however, seems 
to be from the drinking water (Fig. 179) which has become 
infected from sewage or from leakage from water closets. 

Freezing does not always kill the germ of typhoid fever, 
but boiling does. All suspected water should be boiled before 
using. Milk may become infected with the bacillus of ty- 
phoid fever; it is, therefore, best to sterilize it or boil it 
before using. 

It is claimed on good authority that in the late Spanish 
war that the house flies were the carriers of infections from 
the contaminated latrines of the soldiers to their food. Flies 
often become the means of infection, and should be kept from 
the sick-room. 

Scarlet Fever. — There is little doubt that this disease is 
due to a specific genu, and its infection may be carried from 
person to person. It is chiefly spread by the discharges from 
the nose, mouth, and throat, and probably also by the minute 
scales which are thrown off from the surface of the body. 
This disease is much to be dreaded, not only on account of 
the disease itself, but also from the diseases which follow as 
complications. Do not be deceived by the term " scarla- 
tina ; " it is scarlet fever, and treat it as such. Isolation and 
disinfection are imperative in this disease. Any case of rash 
or breaking out should be looked upon with suspicion, and 
the isolation of the person, until its nature is determined by 
a physician. Such cautions are necessary to the prevention 
of epidemics. In scarlet fever, and even in diphtheria, a 
close watch should be made of the urine of the sick person 
so as to catch the first symptoms of albuminuria, which may 
follow as complication in this disease. (For tests of the 
urine see Table of Tests.) 

Measles. — This is an infectious disease, and may be 
spread from person to person either directly or indirectly. 
The patient should be carefully watched to prevent taking 
cold, as this may bring on serious complications. Persons 
are not likely to have this disease more than once. Isolation 
and disinfection should be enforced. 



5fiouj 


Water m Wells 


, and Sickness from 


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ver in Jiiehgan. 


& 


By months, for a period of /# years, mtand ISfO^Z, the re- 


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ation of Sickness from JyfihoidJeuertotiierise and fall 'ofwafa 


• M 


&*<" 


n wells, in Michigan. (The dejtthafthe. wafer in wells f and the defith e 
arik ahove ihe a/afer was reported by observers at from I to ? Stations.) 


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Sickness from Jyfchoid Jever. 



..Groundwater* 



Fig. 179. 
* Indicating what per cent of all reports received stated the presence of 
typhoid fever then under the observation of the physicians reporting. 

The danger from typhoid fever is greatest in October, when the water in wells 
Is lowest, and least in April, when the water in wells is highest. 
492 ( Michigan State Board of Health). 



COMMUNICABLE DISEASES. -493 

Whooping Cough. — This is a communicable disease, and 
in the State of Michigan causes more deaths than does small- 
pox. This is true in most States. It is spread from person 
to person directly, and probably indirectly. ]n most cases no 
special treatment is needed except care to prevent the child 
from taking cold. If, however, the paroxysms of coughing 
are very severe, and weakening to the person, the physician 
should be called. One attack of this disease generally im- 
munes the person from future contagion. The same rules in 
regard to isolation and disinfection should be observed as in 
other contagious diseases. 

Smallpox. — This is generally looked upon as one of the 
worst of contagious diseases, and so it would be were it not 
for vaccination and our present successful methods of treat- 
ing this disease. Measles and whooping cough cause many 
more deaths than does smallpox. (See Fig. 176.) The 
spread of this disease may be prevented by isolation and 
disinfection. By vaccination and revaccination it may not 
only be restricted, but wholly prevented. 

Revaccination should be had at least once in five years, 
as one vaccination does not immune one for life. It is best 
also to be vaccinated whenever smallpox is prevalent, and cer- 
tainly immediately after one has been exposed to the disease. 

As an evidence of the value of vaccination, the following 
is given: In Germany, in 1871, out of a population of 50,- 
000,000, there were 143,000 lives lost by smallpox; in 
187-1, after the enactment of a law requiring vaccination 
and revaccination, there were but 116 lives lost by small- 
pox, and these cases were for the most part in the towns on 
the frontier, where the law was not so vigorously enforced. 

Only pure bovine virus should be used. This can be ob- 
tained from a physician. In being vaccinated always have 
it done by a skilled physician, and have him watch carefully 
the case. 

Persons suffering from the measles, scarlet fever, erysip- 
elas, or exposure to these diseases, or those suffering from 
skin diseases or eruptions, and teething children, and persons 
not in good health, should not be vaccinated. 

Except in the cases just mentioned, every one, young 
and old, should be vaccinated for his own interest, and that 
his body may not become a breeding place for the distribu- 
tion of smallpox to others. 



494 APPENDIX. 



VI. ACCIDENTS 

Asphyxia. — 1. From Suffocation from Breathing Gases. 
— Treat the person at once, as delay is dangerous. If, how- 
ever, there is gas in the room, move at once to a room free 
from gas, and admit plenty of fresh air. Do not crowd 
around the person. Remove all close-fitting clothing that 
would interfere with respiration. If natural respiration 
has ceased, use artificial respiration, of which the following 
two methods are reliable. 

(1) The Sylvester Method. — Place the person on his 
back on a level plane, slightly inclined from the feet upward, 
and place under his shoulders a firm cushion or a coat or 
quilt folded to serve as a support. Keep the head in line 
with trunk. Draw the tongue forward, and keep it in place 
by means of a handkerchief which is placed across the ex- 
tended organ and carried under the chin, then crossed, and 
tied at the back of the neck. Kneel at the head of the patient, 
grasp his elbows, and draw them upward until the hands are 
carried above the head (Fig. 180, a). Keep them in this 
position until one, two, three, can be slowly counted. This 
produces inspiration, as it elevates the ribs, expands the 
chest, and thus produces a rarefaction of the air in the 
lungs and inrush of the air. The elbows are then gradually 
carried forward, downward, placed by the side, and pressed 
inward against the chest (Fig. 180, b). This lessens the 
capacity of the chest, causing an outflow of the air, i. e., an 
expiration. These movements should be repeated about fif- 
teen times per minute, and kept up until natural respiration 
is restored, or as long as there remains any signs of life. The 
Sylvester Method is not successful in asphyxia of very young 
children, as the pectoral muscles are not sufficiently de- 
veloped. 

(2) The Marshall Hall Method— The patient is first 
placed face downward, the head resting on the forearm and 
chest, supported by a roll or pillow. He should then be placed 
on his side. In each of these positions the forearm should be 
held so as to support the head of the patient. The mouth of 
the patient should be kept open, and the tongue prevented 
from falling back. Repeat the movements at intervals of 
two or three seconds. Cease the use of the artificial respira- 



ACCIDENTS. 



495 




Fig. 180 a. — Resuscitation. Inspiration. (Brinckley.) 




Fia. 180 6. Resuscitation. Expiration. (Brinckley.) 



496 APPENDIX. 

tion as soon as natural respiration begins, unless the efforts* 
are feeble or imperfect. Do not permit the patient to be- 
come chilled, but keep the body warm by friction and warm 
applications. As soon as the patient can swallow, give warm 
milk, coffee, or hot water. As soon as possible, put the pa- 
tient in a warm bed; watch him to prevent any relapse, at 
the slightest indication of which, friction, and even artificial 
respiration, may be used. Give volatile stimulants, as am- 
monia, aromatic spirits of ammonia, or ether. Keep the 
patient quiet for some time after recovery. For adults the 
Sylvester Method is the better. 

2. From Drowning. — Rule 1. Remove all obstructions 
to breathing. Instantly loosen or cut apart .all neck- and 
waist-bands, turn the patient on his face, with head down 
hill ; stand astride the hips, with your face toward his head, 
and lock your fingers together under his belly ; raise the body 
as high as you can without lifting the forehead off the 
ground (Fig. 181, position 1), and give the body a smart 
jerk to remove mucus from the throat and water from the 
windpipe; hold the body suspended long enough to count 
slowly, One, two, three, four, five, repeating the jerk more 
gently two or three times. 

Rule 2. Place the patient on the ground, face down- 
ward, and maintaining all the while your position astride the 
body, grasp the points of the shoulders by the clothing, or, 
if the body is naked, thrust your fingers into the armpits, 
clasping your thumbs over the points of the shoulders, and 
raise the chest as high as you can (Fig. 182, position 2), 
without lifting the head quite off the ground, and hold it 
long enough to count slowly, One, two, three. Replace him 
on the ground, with his forehead on his flexed arm, the neck 
straightened out, and the mouth and nose free. Place your 
elbows against your knees, and your hands upon the side of 
his chest (Fig. 183, position 3), over the lower ribs, and 
press downward and inward with increasing force long 
enough to count slowly, One, two. Then suddenly let go, 
grasp the shoulders as before, and raise the chest (position 
2); then press the ribs, etc. (position 3). These alternate 
^movements should be repeated ten or fifteen times a min- 
ute for an hour at least, unless breathing is restored sooner. 
Use the same regularity as in natural breathing. 

Rule 3. After breathing has commenced, restore the ani- 



ACCIDENTS. 



497 




Fig. 1S1.— Treatment of the Drowned. Position 1. (Brinckiey.) 




Fig. 181.— Treatment of the Drowned. Position 2. (Brinckiey.) 




Fig. 181.— Treatment of the Drowned. Position 3. (Brinckiey.) 



498 APPENDIX. 

mat heat. Wrap him in warm blankets, apply bottles of hot 
water, hot bricks, or anything to restore heat. Warm the 
head nearly as fast as the body, lest convulsions come on. 
Rubbing the body with warm cloths or the hand, and slap- 
ping the fleshy parts, may assist to restore warmth, and the 
breathing also. If the patient can surely swallow, give hot 
coffee, tea, milk, or a little hot sling. Give spirits sparingly, 
lest they produce depression. Place the patient in a warm 
bed, and give him plenty of fresh air; keep him quiet. 1 

The Sylvester Method may also be used for resuscitation 
from drowning. The mucus should first be removed from 
the mouth by means of a towel wrapped around the fore- 
finger, and the water from the throat by placing the body 
on the face and lifting it by the hips so the water will run 
out. This should not take over four or five seconds. 

Bleeding, or Hemorrhage. ■ — Bleeding from an artery is 
shown by the bright scarlet color of the blood, and its flow- 
ing in jets; that from a vein, by the blood being of darker 
color, and not flowing in jets ; that from the capillaries, by 
oozing of the blood from several points. 

If the injured vessel is a large artery, it should have 
immediate attention, as there is great danger from the loss 
of blood. Place your finger on the spot from which the 
jet comes, exerting sufficient pressure to prevent the flow, 
and elevate the limb. As soon as possible, apply pressure 
by means of a field tourniquet, which should be placed in 
the course of the vessel. If it is an artery, it should be 
placed between the wound and the body; if a vein, beyond 
the wound. A field tourniquet may be made by taking a 
square piece of cloth or handkerchief and twisting it corner- 
wise, and tie a hard knot in the middle. The knot should 
be placed over the injured vessel a few inches from the 
wound, carry the ends around the limb, and tie loosely. 
Place stick between the tied end and the limb, and twist 
the bandage until the finger can be removed from the com- 
pression without a return of bleeding. Keep the patient 
quiet. 

Get a surgeon at once. If a surgeon cannot be secured, 
by means of a tenaculum draw the injured blood vessel 
from the wound, and tie a silk or linen thread around the 

i Rules 1, 2, and3 are taken from the Bulletins of the State Board of Health 
of Michigan, by their permission. 



ACCIDENTS. 499 

.vessel between the tenaculum and the flesh. If you do not 
have a tenaculum, use a pair of small tooth pincers. Tie the 
thread with a w> reef knot," allowing the ends to hang out 
of the wounds. The tourniquet may now be removed. Wash 
the wound, apply ice or hot water to the small bleeding- 
points, and so bandage the parts as to draw the wound 
together. Let the injured part rest on an easy pillow or 
cushion covered with oiled silk, oiled paper, or India rubber. 
Leave in this condition for forty-eight hours, unless bleeding 
again occurs. The wound should be redressed the third day. 
The stiffened cloths should be first softened with tepid water. 
Wash the wound with warm water. The water may be anti- 
septicized by first boiling it and allowing it to cool to the 
desired temperature, and adding a few drops of carbolic acid. 

In case of a small vein or artery, elevate the part, and 
wash. Ice water or water at 46° to 49° C. may now be 
applied. The part should be exposed to the air. The nat- 
ural contraction of the artery, with the coagulation, will 
control the flow, and prevent further bleeding. 

Bleeding from the Lungs or Stomach. — The blood from 
the lungs is bright red, frothy, or " soapy," and generally 
small in amount. The hemorrhage usually follows cough- 
ing; the blood feels warm, and has a salty taste. Lie in 
bed on the back, and be quiet. While this is a very grave 
symptom, do not become excited; courage and rest is of vital 
importance. Loosen all tight clothing, keep the shoulders 
well raised, and the body in a reclining position. Bits of 
ice should be eaten freely, or alum may be held in the 
mouth, and swallowed very slowly until the bleeding is 
stopped for the time. Do not give alcoholic drinks, as these 
tend to dilate the arteries and to counteract the action of the 
styptics used. 

Bleeding from the stomach is characterized by nausea, 
the blood thrown up is dark, not frothy, generally larger in 
amount than from the lungs, and generally mixed with food. 
The patient should be placed in a horizontal position, and 
on his back. It may be treated in the same way as a bleed- 
ing of the Lings. 

Food should be taken in small quantities, and in a con- 
centrated form. A good home remedy for hemorrhages is 
cinnamon tea ; especially is it good for intestinal hemorrhage, 
and some other forms that cannot be mentioned here. 



500 appendix:. 

Bleeding from the Nose. — While this form of bleeding 
is most frequent, it is not, as a rule, dangerous, but rather 
in many cases a benefit. It is, however, sometimes quite 
difficult to control. Let the patient sit erect; do not lean 
forward, as this tends to increase the hemorrhage. Dip two 
cloths, of convenient size, in cold water, wring out part of 
the water, and wrap one around the neck and the other 
around the forehead and upper part of the nose. Do not 
blow the nose. 

To a cup of water add a tablespoonful of powdered alum, 
and use as a snuff. If this does not stop the bleeding, make 
a plug for the nostril of absorbent cotton soaked in the alum 
water. 

Fainting,, — Have the patient lie flat on the back, and 
loosen all tight clothing. Dash cold water in the face. Hold 
smelling salts or ammonia to the nose. Rub the limbs, so 
as to force the blood toward the heart. As soon as aroused, 
give a dose of aromatic spirits of ammonia, thirty to sixty 
drops, in a third of a glass of water, or a drink of hot milk, 
coffee, or tea. 

Fractures. — In case of broken bones, call a surgeon at 
once, and give him the control of the case. If, however, the 
case is such that immediate attention must be given, deter- 
mine as near as you can the nature of the injury. Loss of 
power to use the limb, pain, and swelling, indicate a broken 
bone. Handle the parts with great care and tenderness. 
Make temporary splints from pieces of board, pasteboard, 
or bark, first padding the parts with any soft substance that 
is at hand, and bind the splints together by strips of cloth, 
pieces of handkerchiefs or suspenders. Put the limb in as 
comfortable a position as possible. In case it is a broken 
arm, support it, after the splints have been put on, by a 
sling. 

Sunstroke. — This condition is more properly called 
" heatstroke. " The person falls suddenly, as in fainting, 
from which it may be told by the head being hot. Take the 
patient to the shade, and bathe the head and face in cold 
water. Mustard plasters may be applied to the spine and 
stomach. Keep the patient quiet until fully recovered. 

Shock. — This may result after a severe injury or from 
great fright. The patient becomes cold, the pulse feeble and 
slow; the skin clammy and bloodless; the respiration slow 



APPARATUS AND REAGENTS. 



501 



and very gentle, and sometimes it may come in gasps; the 
eyes dull. The patient may be semi-conscious, or fully so. 
Restore the warmth to the body, either by friction or warm 
applications. Hold smelling salts or ammonia to the nos- 
trils. As soon as the patient can swallow, give hot water, 
hot milk, or coffee. 



VII. APPARATUS AKD REAGEXTS. 1 



The following estimate is made for a class of twenty. 



Absorption Cotton (common). 
Apparatus for warming stage (1). 
Apparatus. Levers (1). (See Fig. 

34a.) 
Beakers, Griffin's, with lip, 60 c.c. 

( 2 doz. ) . 
Bell Glasses, low form, 4-in. (2 

doz. ) . 
Bone Forceps ( 1 ) . 
Bone Saw ( 1 ) . 

Boxes for Experiments ( 20 ) . 
Bulb Syringe (1). 
Bunsen Burners (if there is a 

supply, ( 20 ) . 
Chemical Thermometer, graduated 

to 200° C. (3). 
Circular Covers No. 2, % in. in 

diameter (1 oz. ) . 
Circular Covers No. 

diameter (1 oz.). 
•Clinical Thermometer ( 1 ) . 
Compound Microscope, 

Bausch & Lomb ( 1 ) , 



gas 



2, y s in. in 



B.B.4, 
(See 

Fig. 175.) For bacteriology 

use, B.B.7. 
Dissecting Board, 20x36-in (4). 
Dissecting Microscope, Barnes 

(20). 
Dissecting Set, in case ( 1 ) : — 

1 Scalpel ; edge 45 m.m. 

1 Scalpel ; edge 25 m.m. 

1 Scissors; medium, straight. 

1 Forceps; heavy, straight. 

1 Cartilage knife; all steel, 
edge. 45 m.m. 

1 Tenaculum. 

1 Triple Chain and Hook. 

1 Blow Pipe. 



•Dissecting Set (incase) (20): — 
1 Scalpel; edge 38 m.m. 
1 Scissors; medium, straight. 
1 Forceps; blunt blades. 

1 Forceps; fine, curved points. 

2 Needle Holders and Needles. 

Droppers (or bulb pipette) (20). 

•Drying Oven ( for air ) ( 1 ) . 

Evaporating Dishes, lG-oz. porce- 
lain (2). 

Evaporating Dishes, 4-oz. (20). 
Filter Paper, 6-in. (3 pkgs.), 8-in. 

(1 pkg.). 
Flasks, flat bottoms, 32-oz. (4). 
Flasks, flat bottoms, 16-oz. (G). 
Flasks, flat bottoms, 8-oz. (20). 
Funnels, glass, 6-in. (2). 
Funnels, glass, 4-in. (20). 
•Freezing Apparatus Attachment, 

for simple microtome ( 1 ) . 
Glass Squares, 5x5 in. (6). 
Glass Squares, 3x3 ;.n. (20). 
•Graduated Cylinders, 250 c.c. ( 1 ) . 
Graduated Cylinders, 100 c.c. (2). 
Graduated Cylinders, 25 c.c. (20). 
Hessian Crucibles (small, not over 

1 oz.). 
Imbedding L's ( 1 doz. ) . 
Imbedding Trays, porcelain, 4x4 

in. and 3 in. deep (20). 
•Injection Apparatus (No. 2127), 

(Bausch & Lomb) (1). 
Injection Apparatus, cheaper form 

(No. 2126, B. & L.) (1). 
Jars. Glass, qts. ( 10) . 
Jet Tubes, one-way ( 6 ) . 
Jet Tubes, two-way Y-shaped 

(6). 



i Articles marked with a star (*) may be dispensed with, if economy is 
required. 



502 



APPENDIX. 



Microscope Object Slides (5 

> gross ) . 
*Microtome, Minot's or Bausch & 
Lomb's No. 2400 F. 

* Microtome, student's (in place of 

the above ; a cheaper form ) . 

Microtome, simple. 

Microtome Knife or Razor ( 1 ) . 

*Muscle Curve Apparatus (com- 
plete ) . See Fig. — . 

Pith, elder or mullein. 

Platinum Foil 3 cm. by 4 cm. (4 
pieces). 

Pulley, small (4). 

*Scales, Apfel's Improved Triple 
Beam No. 1. 

^Skeleton, human (articulated). 

*Skull, human (disarticulated). 

Set Reagent Bottles. 

Spatulas, steel blades, 4-in. (2). 

Sponges, coarse, large (6). 

Spirit Lamps (20). 

Test-Tube Racks (20). 

Test Tubes, 8-in. ( % gross). 

Test Tubes, 6-in. ( 1 gross ) . 

Test Tubes, 4-in. (1 gross). 

Tubing, soft rubber, 3-16 in. diam- 
eter (20 ft.). 

Tubing, hard rubber, 3-16 in. diam- 
eter (20 ft.). 

Tubing, glass, -3-16-in. (2 lbs.). 

Turn Table (1). 

U-tubes (% doz.). 

*Watch Glasses, Syracuse, solid. 

* Water Bath, Naples (simple 

form ) . 

* Weight, iron (% to 32 oz.). 

REAGENTS. 

Acid — 

Acetic 3 lb. 

Carbolic ( phenol ) 8 oz. 

Chromic 1 lb. 

Hydrochloric (muriatic) .. .6 lb. 

Nitric (aqua fortis) 6 lb. 

Oxalic 4 oz. 

Picric 4 oz. 

Sulphuric ( oil of vitriol ) . . 8 lb. 

Tannic 2 oz. 

Alcohol — 

Methyl (wood spirits), for 

lamps if needed 2 gal. 

Ethyl (spirits of wine or 

common alcohol ) 3 gal. 

Ammonium Hydroxide (aqua 

ammonia), 28 per cent...l gal. 

Ammonia Carmine 8 oz. 

Ammonia Chloride 4 oz. 



Ammonium Chloride 4 oz. 

Ammonium Molybdate y± oz. 

Ammonium Potassium Bichro- 
mate 2 oz. 

Antimony (metallic powder- 
ed) 1 oz. 

Agar-Agar 1 lb. 

Arrowroot . . . . 2 oz. 

Baking Powder % lb. 

Balsam, Canada (in benzole) y 3 pt. 

Barium Chloride „ 4 oz. 

Beef Extract (Lieb's), 4 oz. (can) 

Benzene 1 lb. 

*Bismarck Brown . y 8 pt. 

Bismuth Hydroxide 2 oz. 

Brunswick Black . 14 pt. 

*Borax Carmine (Grenadier). 

Canada Balsam. (See Balsam.) 

Carbolic Acid. (See Acid.) 

Carmine 2 oz. 

Carron Oil (for accidents 
from burns or acids) y 2 pt. 

Chlorine Water ( make as 
needed 1 pt. 

Chloroform 1 lb. 

Chromic Acid. (See Acid.) 

Clove oil (see Oil) y 8 pt. 

Collodion 4 oz. 

Copper ( metallic wire or turn- 
ings) 4 oz. 

Copper Sulphate (Blue Vit- 
riol ) 4 oz. 

Cotton Wool 2 lb. 

Cream of % Tartar ( see Potas- 
sium Hydrogen Tartrate) .4 oz. 

Dammar (in benzole) 1 pt. 

Eosene y 8 pt. 

Ether ( sulphuric ether ) . . 1 lb. can 

Fehling's Solution (see Glos- 
sary) % pt. 

Ferric Chloride 2 oz. 

Ferrocyanide of Potassium 
(see Potassium). 

Ferricyanide of Potassium 
( see Potassium ) . 

Formalin 1 gab 

Frev's Carmine (see Carmine). 

Gelatin 1 lb. 

Gibbe's Double Stain for 
Bacillus % pt. 

Glycerine 4 oz. 

Gold Chloride (5 per cent 
solution) % pt. 

Granulated Zinc. ( See Zinc. ) 

Gum Camphor 1 oz. 

Hsematoxylin — 

Grenadier's % pt. 



APPARATUS AND REAGENTS. 



503 



♦Double Stain. Weigert's 

| Solution 1 an<P[I) % pt. 

Hydrochloric Acid. (See Acid.) 

Hvdro<ren Disoaium Phos- 
phate 2 oz. 

Hydrogen Peroxide (dioxide) 
(U. S. P. sol.) 1 lb. 

Hydrogen Sulphide (make as 
"needed) 1 pt. 

Iodide of Potassium (see Potas- 
sium) 

Iodine 1 oz. 

Iodized Serum Vi pt. 

Iron Sulphide 1 lb. 

Lead Acetate (sugar of lead) 8 oz. 

Lime Water (make as need- 
ed) % gal. 

Litmus (in cubes or pow- 
dered) Vz oz. 

Litmus Paper — 

Red 10 sheets 

Blue 10 sheets 

•Loefflers Methylene Blue, for 
bacillus Vs pt. 

Magnesium Sulphate 4 oz. 

Manganese Dioxide (black ox- 
ide) 1 lb. 

Mercuric Chloride 2 oz. 

Mercuric Nitrate 2 oz. 

Mercuric Oxide (red oxide), 
(red precipitate) 4 oz. 

Mercury ( metallic ) 1 Id. 

Milton's Reagent V± pint 

Nitric Acid. (See Acid.) 

Nitrate of Silver. (See Silver.) 

Normal Salt Solution. (See Solu- 
tion.) 

Oil of Cloves Vs pt. 

Oil, olive ¥i pt. 

Oil of Turpentine Vs pt. 

Oxalic Acid. (Sec Acid.) 

Pancreatin % oz. 

Paraffin. 45° C 3 lb. 

Paraffin, 53° C 1 lb. 

Pepsin V-i oz. 

Persulpnate of Iron 2 oz. 

Picric Acid. (See Acid.) 
•Picrocannine (Weigert^ . . . 1 -j pt. 

Platinum Chloride (PtClJ, 

2-per-cent solution V* pt. 

Potassium Acid Tartrate 4 oz. 

Potassium Chlorate 8 oz. 



Potassium Chloride 2 oz. 

Potassium Dichromate (bichro- 
mate) 4 oz. 

Potassium Hydroxide (caustic 

potash) (sticks) 1 lb. 

Potassium Iodide 2 oz. 

Potassium Ferrieyanide ....2 oz. 
Potassium Ferrocyanide ....4 oz. 

Potassium Nitrate 2 oz. 

Potassium Permanganate ...4 oz. 
Potassium Pyroantimonate. .2 oz. 

Silver Chloride Vs oz. 

Silver Nitrate (lunar caus- 
tic) Vs oz. 

Sodium Bicarbonate 4 oz. 

Sodium Carbonate 4 oz. 

Sodium Chloride 4 oz. 

Sodium Hydroxide ( caustic 

soda ) ( sticks ) 1 lb. 

Sodium Sulphate (Glauber's 

salts) 4 oz. 

Sodium Sulphide 2 oz. 

Solution of Acetic Acid, 3 per 

cent 1 qt. 

Solution of Alcohol, 40 per 

cent 1 gal. 

Solution of Alcohol, 60 per 

cent 1 gal. 

Solution of Alcohol, 80 per 

cent 1 gal. 

Solution of Ammonia, 10 per 

cent 1 gal. 

Solution of Chromic Acid, 2 

per cent 1 pt. 

Solution of Gold Chloride (see 
Gold Chloride). 5 per cent. 

Solution, Fehling's % pt. 

Solution, Mercuric Nitrate 

( acid ) Vi pt. 

Solution, Mercuric (neu- 
tral) y 2 pt. 

Solution, Normal (salt), 6 
per cent of salt 1 gal. 

bynthol 1 gal. 

Tannic Acid. (See Acid.) 

Tincture of Guaiacum (gua- 
iac) Vs pt. 

Tincture of Iodine Vs pt. 

Turpentine, Oil of. (See 0/7.) 

Turpentine, Spirits of 1 gal. 

Zinc, Granulated 1 lb. 

Zinc, White Cement Vs pt. 



504 



APPENDIX. 



VIII. BOOKS FOR KEFERI^ce. 



Anatomies. — Gray, Hertzmann, 
Quain, Morris, Henle, Holden. 

tirvsiologies. — American Text- 
Book of Physiology, Howell; Text- 
Book of Physiology, Foster; Text- 
Book of Physiology, Landois and 
Stirling; Animal Physiology, 
Mills ; Comparative Physiology, 
Mills; Hand-Book of Physiology, 
Kirke ; Human Physiology, 
Schenck and Giimber. 

For Laboratory Guides. — Prac- 
tical Physiology, Foster and 
Langley; Anatomical Technology, 
Wilder and Gage ; Dissection of the 
Dog, Howell ; A Laboratory Guide 
in Physiology, Hall; Physiology 
Praciicums, Wilder; Zootomy, 
Parker; The Microscope and Mi- 
croscopical Methods, Gage; The 
Microtomist's Vade-Mecum, Lee ; 
The Micrographic Dictionary, Grif- 
fith Henfrey; Illustrated Diction- 

r 



ary of Medicine, Gould; Text-Book 
of Normal Histology, Persol ; Ele- 
ments of Histology, Kline; Essen- 
tials of Histology, Schaeffer; 
Aquatic Microscopy, Stoke. 

Periodicals. — Journal of Applied 
Microscopy, Bausch and Lomb Op- 
tical Co., Rochester; American 
Journal of Microscopy and Pop- 
ular Science, New York; Anat- 
omischer Anzeiger, Jena; Interna- 
tional Journal of Microscopy and 
Popular Science, London ; Journal 
of Anatomy and Physiology, Lon- 
don and Cambridge; Journal of 
the Royal Microscopical Society, 
London. 

Hygiene. — Hygiene of the Sick- 
Room, Canfield; Hygiene and Pub- 
lic Health, Parkes; Treatise on 
Hygiene, Stevenson and Murphy; 
Ventilation and Heating, Billings; 
Practical Dietetics, Thompson. 



AUG 1 l 1902 



1902 



